I have gotten tips from writing magazines that stress you should have a back story. That is what helps to drive the characters in your story and to give them depth. When you socialize with people, you act upon the experiences and knowledge you have from your past so why wouldn’t your characters do that as well.
Look at the picture of this character and prepare a back story for her.
Where did she come from? Does she have a family? What drives the character?
Freelance Writer and Book Reviewer