I usually start with a random sim, random traits, etc. I'll let 'em go from there. Sometimes I will make them uglier than normal, sometimes they'll look like rockstars. They do get a full clothing tweak if they look silly. (bee hood and swimsuit, no thanks!) :wink:
As for Generational playthroughs - It's always the youngest child that becomes Heir, unless I am doing a gender specific legacy. So if I happen to have six kids, the baby grows up and it allows the parents to age up to Elder. Sometimes they have a career, sometimes not. Agespan is normal. I usually have around four kids just to see the genetics at work. And the family always has a horse or three :blush:
Most recently, however, I downloaded Glenvale County just to see if I *could* make a neighbourhood from scratch. It's extremely challenging. I placed sims I'd saved in my Bin and in CAS and basically just let my mods take over. It's interesting to see all of the offspring of So-and-So - usually they're okay. I delete/change any "pudding faced" NPCs though because they get annoying when they move into homes that I have set up for my sims. The houses are . . . interesting, I've built them from scratch too. It's a neat Sim experiment, but I am having a ton of fun with it :)