Guy Kawasaki reviews a book about being a more civilized employee and gives some excellent tips on being a better person. As usual, his advice can easily be applied in non-business areas, because it’s all about interpersonal interactions.
The golden rule of Jesus really works well to avoid assholishness: treat others how you want them to treat you (no ifs, ands, or buts).
In particular, I like how he emphasizes humility in overcoming assholishness (that’s a word, right?) It’s a tough challenge to face ones past, but it’s worthwhile. You’ll (hopefully) experience healing when you show courage before that which owns you. Letting things in your past define your present is no way to live.
His advice on dealing with work jerks is sound as well: be hopeful and careful. I can’t help but think of The Art of War when I read his advice. It’s all about knowing your environment and the people you deal with and the games they try to play. With proper knowledge situations become easier to avoid (and control, if that’s what you want to do).