Before you criticize, look in a mirror
When I notice something I don't like in other people, I immediately look for that same trait in myself.
One reason for this is that I notice how often people criticize others for being some way they themselves are. I don't want to be like that.
For example, I know someone who says she hates sneakiness and when people talk about others, but she's the sneakiest, most backstabbing person imaginable.
Well, I don't like jealous, control freaks who archate. So I try to make certain I'm not disliking people who are just like me.