I don't think this thread need alot of details as the question speak for itself. It's something Im trying to figure out myself.
Because Ive a rather large population (over 300 playable) so this kind be a bit of a task especially when I don't really use CC for this, except for replacement and re-color and some more option for makeup for the girls, it make it sometimes a bit difficult to keep each sim different from each other, so here is a little survey. It's general thread, not a "what-should-they-wear" one!

1st question: As far as makeup, jewelry, hairstyle and clothes goes - how often do you change these on your sims, like regulary, or do you not bother and let them wear the stuff they get when growing up (with minimal fixes)?
2nd question: Do you try to match their clothes and makeup/hair to their personality, lifestyle or the enviroment they live in?
3rd question: Do you mind having sims that looks very similare or do you make all your sims appearance different. IF you were not using tons of CC, how do you do it?

1) These may change often depending mostly on the recent events in the game. Sims that feel a sense of betrayal, sadness or anger will often wear piercings, and dye their hair a different colour for example.

2) This intertwines with both number 1 and a Sim's wealth and cultural background.

3) One finds similarities will happen regardless of whether a person tries to avoid it or not. This same occurrence can happen in reality where two people look similar, despite having no relations.

1st question: As far as makeup, jewelry, hairstyle and clothes goes - how often do you change these on your sims, like regulary, or do you not bother and let them wear the stuff they get when growing up (with minimal fixes)?
I almost always fix their clothing, a lot of times I fix their hairstyles too - though some sims get a certain hair style as a toddler and just keep it, but it's rare. Make up - once put on, rarely gets taken off or changed, unless I feel like their personality has changed.

2nd question: Do you try to match their clothes and makeup/hair to their personality, lifestyle or the enviroment they live in?
All the time. It's less about their actual personality points and more about how I feel their personality is though. Like I'm not just going to dress a grouchy sim in all black because they're grouchy. Some of their clothing preferences are influenced by parents or older siblings. Though most sims wear what would be considered normal clothing, such as t-shirts, jeans, jackets etc. - Speaking of jackets, I also sometimes change clothes based on weather. Not all the time, but for example when it was Winter for the Newson's and I looked at poor Ginger's clothing and thought "She'll freeze in that!" so I changed her outfit to a sweater and jeans.

3rd question: Do you mind having sims that looks very similare or do you make all your sims appearance different. IF you were not using tons of CC, how do you do it?
I use a lot of geneticised skintones as well as a reasonable amount of custom hairstyles and clothing. However once I invited the Tinkers and the Dreamers to a wedding (between Melody & Dirk) and I noticed that Dean Dreamer and Ronald Tinker have the same hair, both blue clothing and the same skintone. So I had to change Ronald slightly. I claimed it was because in his later child stage so he wouldn't wear a shirt with trucks on it anymore - but really it was just because I thought it might be confusing. Tabitha Traveller and Wendy Langerak also look similar - they had the same hair in the same colour, so I gave Wendy a different hairstyle similar to the first but different enough that I could easily tell the two of them apart - although being that I use a megahood, there's quite a lot of genetics in there, so no-one has the same face, so I guess I could always tell them apart when zooming in.

1) I mostly only change a sims appearance when they age up. I'll give them a hairstyle that suits their personality and sims can't wear make up until they are teens, at least. Some might get new clothes and change those later on, if I am unsure of what image suits their personality better.

2) I mostly change their clothes to suit the personalities, sometimes their wealth will come into it a little as well.

3) No two sims in my neighbourhood are allowed to have the same hairstyle. Especially the females, I have so much CC hair that doing it this way encourages me to use it all. Most sims also have their own individual clothing style as well. If my sims look similar it is down to their genetics and being related and therefore, unavoidable.

Bigsimfan12
I was refering to similarity when it comes to hair, makeup, beard etc, not skintone and genetic features. :P
....though it would be nice if you change your face without surgery via the mirror.

For some reason, my female sims who will work in the education track always end up having the same bob hair and suit-ish outfits. Even if they have different genetics, they can look very similare sometimes.

This is a personality thing. Some sims have a defining look, and some do a lot of experimenting, or even playing with it. Some people are easygoing and allow other people to talk them into different hair and outfits. ("Oh, come on! It'll be fun! And I really need that hairstyling badge!")

Dior Skirt is a fashionista and changes clothes every day, sometimes twice, plus he plays with hair - his own and anybody's within range. Bad News Beverley Spitzig changes clothes every day and changes her hairstyle every day or two unless there's stuff going on preventing her from getting to the beauty store. Red Onions wore the same hairstyle his entire life and changed clothes only on age transition.Most people dress for the weather, wearing long sleeves, layers, and heavy fabric in winter; sleeveless light fabrics in summer; and short sleeves and medium weights in the spring and fall. A lot of people change their color palette somewhat for the seasons, or keep the same colors and change the way they're presented. Tibby Capp is pretty committed to black/brown/white/neutral in her wardrobe, but her spring and summer outfits have smaller, busier patterned and her fall and winter outfits rely on large, solid blocks of color. She also goes for strong lines that make her seem taller and more commanding, in total control of her space. Mikki Dosser also commands the space she's in, but she does it with loose, sloppy clothes that emphasize her sexuality without pandering - Mikki's whole wardrobe says "This is me and I'm sexy and that's my business; I'm not wearing this for you."

College students and teens change their looks the most often, because they're not only experimenting with their looks, they're learning to be themselves. Once they know who they are and how they're comfortable, they can settle down a bit.

It's important for me to know who my sims are from a distance and to tell them apart in the thumbnails. That's one reason why the sims I make myself have exaggerated, cartoony features. But even cartoony features can become confused if more than one sim in an age group shares them, as often happens in the large families I prefer. Silver Beech Hart of the GS Uberhood is a dead ringer for his father Rhett, who looks a lot like his own father Valentine. As long as Silver was a teen or younger he and Rhett could wear the same hairstyle; the moment he went to college their thumbnails became far too similar for this to be comfortable, especially since they tend to share boltage with women. To be absolutely sure I could tell them apart, I changed Rhett's hair and facial hair and gave him glasses shortly before Silver grew up, and then I changed Silver's hair and facial hair when he got to campus. Valentine in this neighborhood has kept his original hair and sideburns all along. When choosing a new hair for Rhett, I had to bear in mind that telling him from Valentine in the thumbnails would be an issue soon. And they also bolt a lot of the same women!

1) Not often.
Many Sims use whatever they got, unless it's absolutely unsuitable - either it does not suit them at all or it does not make sense in the hood context. In those cases they get a new style right away.
Also when they roll a want for new clothes. If they buy them it would make sense to use it.
Other than that rebel teenagers get funky hairstyles now and then, which may later revert to a normal hairdo.
And that's pretty much it.

2) Yep.
But I don't get nuts if - for example - the shy girl gets a mini skirt, I simply assume it's a twist in her story!

3) I don't like having similar Sims at the same time because it confuses me. But I don't mind that they look like a past neighbour, in fact I recently posted this message about two cousins who are almost identical but one is older than the other (teen/child) so there is not possible confussion.
So I don't need tons of CC, simply changing the hairstyle or wearing glasses is enough.

1st question: As far as makeup, jewelry, hairstyle and clothes goes - how often do you change these on your sims, like regularly, or do you not bother and let them wear the stuff they get when growing up (with minimal fixes)?
Everything is personality, skills, aspiration and hobby dependant - so most sims will have to change when they age to teens and I know more about them - the more I play them, the more personality I see, so they often have to update their look to fit with how they seem to be.

2nd question: Do you try to match their clothes and makeup/hair to their personality, lifestyle or the environment they live in?
Definitely - my Italian artist lady, only liked goth and red when I made her in CAS - every time I tried to dress her like a gypsy, she turned up her nose, stamped her feet and looked really upset. So no more gypsy girl, instead she's a promiscuous romance mechanic, hard hearted, who likes, red dress, torn clothes, jewelry and cars and men. Not me fault, her choice not mine. She may change now she's got a toddler that she kind of likes. (she refused to breast feed, first sim woman to choose bottle even though I got a breastfeeding mod set up.

Her husband is a money sim, he looks good in posh suits, but since he likes athletics more, it's tracksuits and tracksuits all the way. He's handsome in his formal suit, but he wears it so rarely. Our town mayor dresses French elegant, the farmer is in casual jeans, and the new money male mechanic, dresses sophisticated urban, cause he likes city living and is a true urbanite metropolitan. If they move house or move jobs or their life changes, they'll get different clothes to reflect their new status.

3rd question: Do you mind having sims that looks very similare or do you make all your sims appearance different. IF you were not using tons of CC, how do you do it?
Like sims to look different, otherwise I get confused and sims start kissing the wrong people. Right now I got a clone problem, every single townie girl has dressed the same this winter. Not sure whether to kill them, redress them, or make a story about a strange cult brainwashing the youngsters.

My problem is, the only sim set up with enough skills and interests to open a clothes shop is also the poorest sim in town, she's renting her house because she spent all her money on posh furniture, and just can't afford to open a dress shop. Next turn, she's gonna get an expensive loan because the sims need dressing and she's the only one that can do that properly right now. Hope she don't go bankrupt again.

If I wasn't using CC.. I would do just the same, except I'd probably use more face paint, makeup and hats to make each sim different. At a pinch, I suppose I'd start having to use a kind of group system.. like anyone wearing facepaint is romance or popularity, all sims wearing goth wear are mechanics,, furs for money sims and artist wear gypsy wear.

The children of wealthy sims do not wear scruffy clothes. If they grow up in rags, I send them to the coathook. Untidy sims have rumpled hair, neat sims go for the short back and sides, or hair piled on top. Outgoing sims need flamboyant clothes and colours; shy sims go for pastels, and try to blend with the wallpaper. Romance sims tend to wear bright lipstick. I don't have many clothing downloads, but all my sims look different. On behalf of elders everywhere, I look out attractive clothing for elders. Faith Goodie usually gets the lavender belted jumper with the floral skirt. She takes off her hat indoors, and has a Marilyn hairstyle and pretty make-up. Her husband gets a Fairisle jumper for working in the greenhouse. Fair play for elder sims!
(Wish I had a lavender belted jumper!)

Amura:
I also find sims with very similare features confusing. Even with hundreds of sims, there is a genetic feature that start to "swallow" a large quantity of the population of Withea Dale. Forget first cousins, in my case, its even FOURTH cousins and unrellatived sims that are almost indentical. It was about that time I start to notice about their appearances where the sims seems to be cursed with one of the face genes from the founders (Ive something like 100 different looking founder sims, still there is one that keep showing up in many of their ancestors....even when adding more "breeding" families to the mix):

"huh? ANOTHER one? With those large lashy eyes and shapely lips?"
...no wonder making them different are a tricky task each generation. I don't use townies so they can only produce with the descendants. Ive about 10 more families (farmers and supernaturals) Im going to add, but then I won't add anymore sims. I wouldn't be suprise that after a couple of generation, almost every other sim has similare features despite the varity from their founders. I don't use CC because my comp can handle too much of it due to a weak processor. :/

EDIT:
PS: This is the cursed gene of the Withea Dale citzen's. Dozen of the newest generation has these features, especially women. Large eyes with thick lashes and curvy tiny lips.
Although it was one of my favorite gene on my sims, its start to the get frustrating when dozen of sims has it. Ive a few others that are dominant and ones I love, but they are not as frequent as this one. Even when changing their hair and makeup, they sometimes confuse me. Since they live in a pre.modern society, I don't like to use plastic surgery to change the look of the sims (except for minor fixes, like eyes are extremly inwards or a very wide gap between lip and nose. which is why I only asked appearance as far as the option via the mirror and closet goes. I use the Gussy Up mod when changing my sims though!). The pic is sims from 2 generations tho:

I know, I just didn't have much to say on the matter Somehow I never manage to have 2 sims look too similar... or maybe they do and I just don't notice because my hoods quite big, and I do tend to pay more attention to a sims hair colour / skintone / genetic features first - I love how genetics play out over time

It's confusing when my sims are a in a career track which makes them have a certain hair style and clothing though... and then they bring a friend home that's also wearing the uniform. I almost had Daniel Bell flirt with Lucy Burb instead of his girlfriend Pauline Aspir because I clicked on the wrong sim.

Bigsimsfan12
I only use defaults for skintone and one set of genetic eyes, so my sims are not so different in that area. 99% of the hairs and clothes are just default replacements as well. But I don't usually have problem with mistaking sim's spouse/lover though. But that have happen a few times. Although they were not similare in appearance,I accidently made a sim woohoo with a hacked bed with his best friend, while he has engaged. So I ended up letting them have an affair. Now these sims are long dead and never knew the "cheating" and half brothers are in good term.

1st question: As far as makeup, jewelry, hairstyle and clothes goes - how often do you change these on your sims, like regulary, or do you not bother and let them wear the stuff they get when growing up (with minimal fixes)?

This is constant for me, I never ever let them wear the vanilla hair or clothes they grow into. I have gone so far to gussy up townies that walk by too. Their toddler and kid hair stay for the duration of the life-stage, teens I change once or twice (girls more than boys) and YA and elder will change about thrice on average, elder will have an early stage of colored hair and then go grey as they get older. I don't change what they wear every day but I will change one or twice a season (which ties into the next question)

2nd question: Do you try to match their clothes and makeup/hair to their personality, lifestyle or the enviroment they live in?
I match their clothes up to the image I have of them. Fancy trophy wives wear expensive cocktail dresses, business women wear professional outfits, men in the lower stages of their career dress pretty casual. Teens who are 'punk' wear dark colors or red and color their hair. Personality doesn't usually affect what they wear - like super nice or super mean sims could wear anything.

3rd question: Do you mind having sims that looks very similar or do you make all your sims appearance different. IF you were not using tons of CC, how do you do it?
I do mind having similar looking sims. I don't like sims of the same life-stage having same hair color and style and I don't think any of mine do (I have a lot of varying looks as a result, ) as well as a butt-load of cc hair.
Of course having jewelry, glasses, and face masks can help vary looks too, and I use them liberally. At this point like 80 percent of my sims were in game born so I don't have control of how similar or different their genes make their faces look, unless they are the type that would opt for plastic surgery.

1st question: As far as makeup, jewelry, hairstyle and clothes goes - how often do you change these on your sims, like regulary, or do you not bother and let them wear the stuff they get when growing up (with minimal fixes)?
Clothing gets changed daily (I'm pretty picky about that). Makeup only gets changed for most sims if they have a personality/dress style that's a little bolder/colorful. Not all sims wear jewelry, so this isn't one that I put too much focus on.


2nd question: Do you try to match their clothes and makeup/hair to their personality, lifestyle or the enviroment they live in?
Always. I like for everything about a sims life (home, sense of style, the colors they are surrounded by) to reflect their personality/perceived personality. I'm big on aesthetics...so things have to be just so in my game.


3rd question: Do you mind having sims that looks very similar or do you make all your sims appearance different. IF you were not using tons of CC, how do you do it?
I like variety, which is why I enjoy playing most of the premades and add in very few of my own created sims. However, while I have no issue playing a sim that is deemed 'unattractive' by some (perfect is boring), I do not like the far out there overly wacky looking sims. I'm more of a realistic player in that sense.

1st & 2nd question: I change their clothes seasonally, and/or when they age up. I'll let them wear what they age into if i feel it suits their personality (and the current season), but the majority get a makeover.

Sometimes i will take a cue from what they pick to wear as they age (esp at teen birthdays) as an indication of their personality/interests - eg the youngest Newson twin always seems to age up into pink frilly things when she hits the child stage, so i figure that's her fave shade and that she's a feminine kinda sim, so i follow that theme with the rest of her wardrobe and as she ages.

Richer sims can afford more clothes (everyone gets a freebee initial makeover in each clothing category), and will get outfits with richer looking fabrics for eg.

Kids, and to a lesser extend teens, are also potentially hindered by their parents tastes. A neat fortune sim with conservative leanings might not allow their kids to wear scruffy and/or counterculture wear. Better save it for college!

3rd question: I do mind them looking similar, but i don't play with a lot of CC, so it's hard sometimes. Lots of similar outfits & hair, just in different shades XD.

I change hairstyles frequently. They get a change once a week for sure, and sometimes during the week. If they are working on charisma, I tend to change their hair every time they finish a charisma session. I figure part of charisma is good self esteem and changing their hair reflects that. Every Saturday the whole household gets a new hair style and acquires new clothes via the buy clothes option on Christianlov's Gussy up. By the way, if anyone knows of an updated version that includes outerwear, please let me know.

They change clothes daily.
Neither is dependent upon their personality. I have OCD so I count to see what they will wear or what hairstyle they will have.

I change fashion themes every decade. I have a list of eight themes (including two slots for freestyle/no set theme), and at the end of each decade I roll 1d8 to see what will be in for the next decade. The current theme is then removed from the list and a new one put in its place. I then set about reclothing my sims in line with the new theme, though I'm not obsessive with this. Some sims will buck the trend, either because their personality suggests they won't go along with the herd, or I don't have anything suitable in their wardrobe and can't be arsed to send them shopping. At some point I might go CC-hunting for gear that fits in with the current fashion.

I usually determine a Sim's style once or twice per lifestage. This is based on the Sim's character I have observed so far and the events that have taken place in their life. For example a Sim adult female would be wearing lots of make up and preppy dresses to go out, but later I would give her a more practical hairdo and clothes because she is managing three kids, two dogs AND a demanding career.

Obviously special events like weddings also get them a makeover. But I never play weddings anyway.

As for the last question: Yes, if a Sim is supposed to have a certain hobby or come from a certain place, then I adjust their looks accordingly. An athletic Sim would wear comfortable/athletic clothes and ponytails/short hair, while a mountain dweller would not be seen in light bikinis and tank tops.

I always have one sim in the household wear the same outfit throughout their entire lives.

1) As a rule, whenever I start a new neighborhood, I'll make over the pre-mades there if their look is unsatisfying to me. Other than that, I only change the clothing once they reach a new stage of life

2) Yes, clothing is set to match their personality or social status

3) I try to make sure no two sims in a hood have the same look, unless it's intentional copying. I have enough CC to manage that for the most part.

1st question: As far as makeup, jewelry, hairstyle and clothes goes - how often do you change these on your sims, like regulary, or do you not bother and let them wear the stuff they get when growing up (with minimal fixes)?
Some of my Sims change their clothes with great frequency. Andrew Jones likes to dress sensibly to school (shirt and tie with grey or black shorts) but usually changes into something more risqué when he gets home, especially if he's going out. But he might then wear the same outfit for the whole weekend. His boyfriend Julian on the other hand just puts on the same pair of skimpy denim shorts and trainers every day. He has an aversion to tops of any kind, and never wears a shirt or a jacket, even to school. Some of my poorer Sims can only afford one outfit, or (like Julian) there's one outfit that they like so much they never wear anything else. A lot of my Sims do change their clothes frequently though, including underwear and swimwear, and visits to clothes outlets are frequent. Hair and accessories, etc. are changed much less often, partially because, as with real people, I tend to recognise Sims by their hair. If a Sim is growing his or her hair, they will tend to go through one or more intermediate stages till it reaches its full length. Birthdays are very rare on my game, but, when they do happen, they are followed by a visit to the clothes shop. The explanation: the clothes they grow up into are the presents that relatives and friends gave then. Then they use their birthday money to buy the stuff they really want. If needed, I think I'd use a money cheat to make sure they had some birthday money to spend! The stuff they grew up into goes into the wardrobe and may even be worn on occasion. "Put on that cardigan that Aunty Maude gave you for your birthday. She's coming to tea."

2nd question: Do you try to match their clothes and makeup/hair to their personality, lifestyle or the enviroment they live in?
Consciously or subconsciously, I think I do this all the time. A lot of my Sims originate in CAS, and when I'm dressing my new CAS Sim, I usually have a good idea of their personality. I give them clothes that I think they'd like to wear. Similarly when my Sims go out to buy clothes, or when I give new clothes to townies who are becoming more involved in the life of the community. Gay males (of whom I have a lot) are more likely to wear pendants round their necks than straight ones. Another strong influence on clothing is fashion. Veronaville is trying to establish itself as a fashion centre to rival Milan, Paris, London and New York. Extreme fashions that you might expect to find only on the catwalk, actually make it onto the streets of Veronaville. In particular this manifests itself in some very revealing clothing being worn by both sexes. Sims in my other neighbourhoods often follow Veronaville fashion.

3rd question: Do you mind having sims that looks very similare or do you make all your sims appearance different. IF you were not using tons of CC, how do you do it?
I like all my Sims to look different so that I can recognise them! Due to work uniforms and fashion fads, several may dress alike, and, unless facial features are very marked, I find them hard to distinguish in normal gameplay. So hair style and colour are really the main way I recognise my Sims. As there are only a handful if Maxis hairstyles that I really like, I use a lot of CC hair, and I think I'd be lost without it. The two most similar looking Sims in my game are both Maxis Sims: Mercutio Monty and Ravi Bertinio (one of the Tricou teens).Try telling them apart when you see them in their trunks at a community swimming pool!


Fortunately Mercutio and Ravi have very different tastes in clothes, and Ravi is much nicer! As a last resort I can always hover the mouse over a Sim if I can't recognise him/her or remember his/her name; I wish I could do that in real life!

1st question: Most of my sims don't wear jewellery but those that do tend to keep it quite awhile. Except Christmas jewellery, that only gets worn for the season. Age up or middle age is when jewellery might get added or changed. Hair style I might change more often. I generally start with hair on infants and that decides how much hair a toddler will start with. A bald infant will have very short hair as a toddler. Half way through toddlerhood (day 4) I might change to a longer hair if the hair was very short. I do the same for kids, they may get a hair change on day 8 or so to show older childhood. Otherwise hair gets changed on age up if I feel it needs changing and again at middle age. Ladies and men get shorter cuts, at this point I decide if a male sim is to go bald. Those that will go bald get a haircut that looks a bit thinner. I tend to change clothes when I change hair, so halfway through toddlerhood, at age up, half way through childhood, at middle age. Sometimes I change clothes based on seasons but I am doing this less with my beach hood since there is no winter. In hoods with winter my sims always get a change of clothes into something warmer. That depends what they age up into. Occasionally I keep it or part of it. One of my YA in my play through grew up into white cargo pants and I let her keep those.

2nd question: Yes, to both.

3rd question: Every sim must look different and I use tons of cc to achieve this.

I always try to pick clothes, accessories and makeup that fits the personality of a sim, at least for stories and pictures.

1) I hardly ever change hairstyles, unless it's needed story-wise. Mostly I just pick one and stick with that. Makeup - same thing, since I rarely use anything else than natural makeup such as freckles or other details. I don't use a lot of jewlery on my sims, and only bother with accessories if it's for storytelling. As for clothes, my storytelling sims change clothes very often, usually every other day or so, story-wise. I usually don't change clothes much on other sims.

2) Most of the time, yes.

3) I usually make sims look very different, and I use lots of CC. Occasionally if play with identical multiplets, they get matchy hairstyles or clothes in their younger years.

1. Most of my sims don't wear make up or jewelry. If they do it matches their outfit/personality
2. Typically I pick clothes that match their personality/the personality i've thought up for them.
3. Most of my sims look the same right now, but it's a start of a town and most of the sims are from the same background. It doesn't bother me considering most people in any one city/town look pretty similar with a few outliers.