Do you create your characters for each story, or do you "meet" them and then tell their story?
Both! Sometimes I have a character in my head that is banging around in my head saying, "Let me out! Let me out!" :P Other times, I improvise. Or a character doesn't turn out the way I planned. I think it's important to give each character depth. Otherwise, you run into Mary Sues and Marty Stus and those people are no fun.