Another important part of creating a character is giving them a background story that makes sense. For example, it is doubtful (although not impossible) that a person coming from an abusive background is going to be a completely stable person with great self-esteem.
Using my book Vampires Rule as an example, I can tell you that I started with the kind of person I wanted Jack to be. He's a bit naiive when it comes to other people and isn't real good at picking friends. I wanted him to be drawn in by the villain, but I didn't want Jack to appear stupid. I knew from the beginning that Jack's parents would be dead when the story started... but what kind of relationship did he have with them? What kind of relationship did he have with his father?
In order for the book to work, I decided Jack would have had a father who didn't show emotion easily. He was more likely to slap his son on the back for a job well done than to hug him or say he loved him. Still, Jack misses that. He misses having that father-figure in his life... then here comes the antagonist. Although the villain is in his thirties, he's charasmatic, intelligent, and knows just what buttons to push to get Jack on his side.
In closing, remember to look at the character's backstory when fleshing them out. It needs to make sense. Think about it. We spend our entire adult lives trying to get over our childhood (unless you had a perfect one, which most of us haven't). Happy writing.