How do you define being non-judgemental?

Interesting subject. It is very difficult to be non-judgmental, but I personally feel there are some things we have to be judgmental on, like for instance if we see someone behaving really badly towards and hurting someone else. I try though on things which are harmless, to be as non-judgmental as I can - it isn't easy at first, but what I do is sit and question what someone else may be doing, and ask myself.... "is this really harmful or bad?". If I decide that it isn't, then I live and let live. Another thing which helps me is to remember the not so good things I've done myself, and think that who am I to judge the actions of another if I can't always do the right thing.