The first rule I believe would be to remember that we ourselves have flaws.
We must understand that not everyone is perfect and that the things that bother us most about others are usually flaws that we have ourselves. And all to often we are ready to overlook those flaws, but we are all to willing to point a finger at someone else's flaws. This is really sad.
Let's face the truth of things, it would be all to easy to go through life focusing only on the flaws of others rather than focusing on the person that looks at us from the mirror every morning. But we must wash our own faces before we can offer the washcloth to someone else.
I feel that if we spent more time fixing our own flaws we would be to busy to see the flaws in those around us.