One of the rules that I always follow is that no matter how crazy characters may act, and no matter how absurd or strange their actions may be, that it's justified in the character's mind why they are doing it. Not to get all heady about it, but it's fun for me to test how far I can go with things while still keeping it grounded enough that you believe that the character really believes that what he's doing will get him what he wants. It's a personal challenge to me to see how far I can go with that.