1. No spamming, profanity, inappropriate content, malicious insults, or language implying insult to a group of people (e.g. "gay" as a synonym for "lame"). Also, don't post links to other sites containing any of the above, especially profanity and inappropriate content.
2. All posts must be in-character in the in-character section of the forum. (Which hasn't been created yet.) OOC posts in places they shouldn't be will be deleted and the perpetrator warned. (Just verbally, not forum-warning-stuff, since that just leads to arguments).
3. This one is very important. NEVER RP another person's character unless they have given you explicit permission to! Small things, like a pretty unimportant conversation, are probably all right, but don't, say, seriously injure someone, make them do something stupid or humiliating, write their dialogue in an important conversation (like the thing with Shawdell/Rhia on MR), etc. If you have any doubts of whether the character's owner would approve of the content, ask them first or don't post it. This is essential to prevent arguments.
4. No Mary Sues or "godmoding". Invincible characters are no fun. Try not to let your character always save the day or steal the spotlight. Give him/her/it/the pirate monkey weaknesses, and let other people get the glory sometimes. This applies especially to mages: other people's talents, like fighting or craftsmanship, are also valuable. And don't make your mage super-powerful or talented; especially, don't make him/her better at fighting through magic than a conventional warrior would be. That kind of thing makes Myra very sad.
5. Try not to double- or triple-post, especially if you have a large avatar or signature that means a lot of scrolling for your innocent victims. Sometimes you have to, especially if lots of people are on at once, and that's all right.
6. Please, please, please don't make a huge and/or obnoxious signature or avatar. Some of the ones in existence right now are pushing it. We don't want to have to scroll past a greater volume of signature than of content.