Yeah, like putting in personality "pops" of your family members! I've got lots of side characters, but they're very, very important. 4 main characters--they have their own personalities. It's kind of easy! Think of your friends at work, school, home--think of who influences you to do good or bad...teachers, people in charge. No one is the same and you don't think or even react the same way to them.
Oh, have fun with them. (Doggonit, did I play with too many dolls in my youth!) 