How to design casual people

Hello, I have a question, how does one design casual people ? It's very nice teqnique with motifs and mirroring shapes to get some interesting combinations and puling out cool armor or creature design, but it doen't work when you need to design lets say 40 years old highschool teacher, is there a technique I could use to help me get ideas fast for things like realistic faces, normal clothes, hairstyles etc ? And in general what makes person unique and rememberable ? ..when you can't stick a hurn on his head and put intrigue spiky armor on top ?