After reading Matticus' post "20 Characteristics of a Mature Guild Member", I realized that those characteristics pretty much summarize what I respect the most in my fellow players.
I feel that there is great wisdom hidden (or in plain sight) there.
So I highly recommend you to check it out, "evaluate" yourself and see if there is room for improvement. I certainly spotted some weak points I have.
(posted on mobile, edited the previous version)