I play my sim with autonomy for a while and see what kind of things that sim does, wants etc. Then I give them the fitting makeover because I kind of have a sense of what personality they have then. I go for colors and outfits that just look perfect on them and fits their personality. I like to send them to meet people and watch how they interact with others. I also keep my eye on their moods, like some sims can do things that get them energized more frequently (without having the trait for it) so that gives me the idea this sim is into sports for example. later when sim ages up I give them the matching trait and sporty outfits. So I kind of let them decide a little on their own and once I have a picture of what they like I take over control. I also take into account where I run across them when I play rotational. Like one sim I would always see at the lounge playing guitar, another one is always at the gym, the other one always at a party etc.
When I decide to build a house or change the interior of their house I often take the colors of the parent/s for main rooms. For the kids rooms I take the colors and hobbies/skills from whoever sim lives in that room. When my sim has a baby I will give them the colors from the parents until I figured out what works better for the child. I do the same with their baby/toddler/kids rooms.
The parenthood pack works in my favor here when the kids ask for advice, I know it's random but I find it really matches their personality in a way. Or these little messages that pop up when the kids are in school. Like principal caught teenage son skipping class because he was consoling a friend. I often get this message for this son and it fits, he would do anything for his best friend and he's been through rough times lately so it's understandable (lmao the line between make believe and believe is getting really slim here xD).
I only do this for sims I play, I don't give townies a makeover unless they marry into my sims families somehow.
