I think the answer to this, along with a lot of answers to human social interaction, is to experience and see more people. I have traveled and lived abroad for the last 10 years, meeting so many different people from different cultures.

I began to see a pattern after meeting enough people, where I would meet someone knew, and my first thought where that they where half my friend from college, and the other half my crazy French friend.

I started becoming non-judgmental after I had meet many, many people, becoming secure enough with myself that I do not feel threatened by a new person judging me, and I think that my degree in psychology helped grease the process.

The biggest quote from one of my professors to help both with judging and dealing with others good/bad/indifferent/angry attitudes of the day

"Whenever you think someone doesn't like you, is judging you, or is even outright belittling you, the thing that you always need to be cognizant of is that they will the majority of the time be projecting their internal state. If they are telling you that they think you suck, most likely they in fact think deep down inside that they suck."

Humans are inherently self centered. We default to thinking we cause all the emotional reactions from people. If you can let go of this innate tendency, and assume that all interactions are a result of their internal state, you will find that you are in a world of people dealing with internal chaos, and that you free yourself from it.

Judging people, I think, is assigning a label to them, when in reality we are all a mix of reasons and causations. That being said, I do have a hard time with some things:

being a bad parent, not taking care of yourself, and always complaining about how hard life is.'