The rules are pretty simple.

1. Post with a list of your characters and the songs that you think match them well. You don't have to know the songs yet, if you don't want to.
2. People reply with suggestions on what they think your characters theme song/s would be.
3. You then find their posts and reply with songs you think match their characters.
4. iTunes and youtube are your friends, remember.
5. Profit.