I got this idea from the quizilla fan fiction forum. Here's what you do.
When posting, answer the question about one of your characters posted by the person above you. After answering the question, make up one your own.
For example:
Person one: What is your character's favorite memory?
Person two: Her grandmother teaching her how to draw. What traits is your character attracted to (i.e. hair color, creativity)?
You need to put the name of the character you're answering the questions for. This game is good for major and minor characters. Good guys and bad guys, it doesn't mater.
I'll start us off!
What is your character afraid of the most?