Just some things that I have noticed here and trying to learn:

• Never down vote other user's post. Just comment about it or flag it.
• Be kind. No one is an expert in everything.
• Answering first is not always the best way, quality ones beat them all.
• Answering in a way which is useful for all future readers and newbies.
• Never miss an opportunity to edit the spelling, grammar or formatting of a post. People don't search for wrongly spelled keywords and it also improves user's chance to get an answer.
• The whole point of Stack Overflow was contribution and not competition. Unfortunately, we follow the latter.

And yea, remember that this user rocks and is one of the best persons on earth :)