Unpredictable. Tough. Inventive. Solitary. Determined. Thoughtful. Defiant. Funny. Tempered. Unstoppable.
These are ten words that define the aspects of a person's character -- what's in what I think of as their personality account. Like money in the bank, these aspects can't be seen from the outside, but they're the stuff that directly shapes an individual's personality, reasoning and lifestyle. They're easy to list, but a lot harder to illustrate. They're not obvious like hair color or body build. The character doesn't walk up to the reader and say, "Hi, I'm John Smith. I'm unpredictable, tough, inventive, solitary, determined and a couple other things, and I'd like you to remember that."
When you put together a character, you have to do more than deposit unpredictable in their personality account. You need to incorporate that factor in what they do. You can tell the reader that your hero is unpredictable all the live long day, but if in the story the reader knows exactly what the guy will do five pages before he does, he's not living off the personality account you've banked for him. When confronted with a choice, the unpredictable character doesn't take the well-travelled or less-travelled path. He walks off the path, builds a new path, or blows up all the paths.
Antagonists need the same sort of account, too, but often they're cast in direction opposition of the protag and even more prone to be walked up to the reader for a recitation, i.e. "Hi, I'm Jane Smith. I'm predictable, weak, unimaginative, social, ambivalent, thoughtless, obedient, dull, untried and subservient." I think it's more interesting to have an antagonist who has just as many admirable qualities as the protag in the bank, because that makes them just as real. My favorite books often have protags and antags who, if not for whatever is keeping them at odds, might have been good friends.
Today's assignment: in comments, list ten words that belong in your character's personality account.