My philosophy in one sentence - Be nice.

“I don't care if you're black, white, straight, bisexual, gay, lesbian, short, tall, fat, skinny, rich or poor. If you're nice to me, I'll be nice to you. Simple as that.”

I've seen this quote attributed to Morgan Freeman and to Eminem.  I don't know who originally said it.  I do know that I agree wholeheartedly with the sentiment.  

Only I would also add "alien, or mutant" because they deserve respect, too.

I've found that the converse is true as well.  If I am nice to you, you will be nice to me.

Of course, there are always exceptions.  Some people are just asses.  But I've been lucky that they have been few and far between.

Wil Wheaton has a similar philosophy - "Don't be a dick".

There is always a choice on how to behave in any given situation.  I've found that choosing to be nice has much better consequences than choosing to be nasty.

 "If you're nice to me, I'll be nice to you. Simple as that.”