I'd add:
When you post, try to think of how you can make a positive contribution to the thread. What information did the original poster want that you can add? What good, rational arguments can you muster to support the opinion you are about to write? It is often easy to identify and name and describe a problem, but it is far harder (and much more useful) to propose solutions to it.
Second, give other people the benefit of the doubt. If you think someone MIGHT be trolling, or MIGHT be insulting you, assume they're not. The worst that can happen is that you'll write a nice post that wasn't really needed.
True... Something I myself should do more.
