Keep It Serious
This isn't the place for YouTube videos, one-answer questions with little to no debate in them or threads with no real topic. If you have nothing to add, say nothing at all or your post will be deleted with no comment on the matter. And if it belongs in a specific section, put it there so moderators don't have to. Necro-bumping is frowned upon, threads will be locked if the addition was needless.
Keep Your Cool
Try not to directly attack the poster of the thread, don't go overboard and refrain from screaming at your monitor. They really don't like it.
Keep It Neat
Huge blocks of text, something everyone can be guilty of, are difficult to read. Try pressing enter a few times, and sometimes draw attention to certain words to make them more important. But all in moderation of course. Large font sizes are discouraged.
Don't reply to horrible threads just to make fun of how horrible they are
If you think a thread is useless, don't bump it by posting in it. That's what Random and Incoherent Babbling is for.
Use descriptive thread titles and post in the right subforum
Seriously. Your post will be moved, or if a moderator is feeling particularly vindictive, deleted.
Conversation
Unless you're replying to the point in a persons sentence using their example, don't comment idly about their avatar or how cool you think someone is, unless it's just in agreement. These posts will slide if they lead back to meaningful discussion, otherwise they may disappear.
Use Your Common Sense
Yeah. I know this encompasses everything, but common sense is practically a modern day superpower.
There are exceptions to these rules and they may be changed at any time without prior notice. They are effective immediately, and are subject to moderator interpretation.