This is a very good set of rules IMO: http://gametoast.com/forums/viewtopic.php?f=40&t=21656
I'd definitely add those to ours:
1. The decisions and actions of the Moderators and Administrators are Final
2. Post Meaningful and Clear Topics and Posts
3. No Religious or Political Discussions
4. Don't play 'Junior Moderator'
5. Be kind to other users and Don't be rude.
6. Avatars must be no bigger than 150 (wide) by 200 (tall) pixels (don't have to be exactly like that but something similar) + limiting (or removing) signatures
7. Limit the Use of Profanity
8. Don't spam (maybe add to 2)
9. No warez of any kind
10. No pornographic content.
11. No forum games? Or only Star Wars related forum games?
And in our case as you said something like 'Giving others a reason to think you're a developer' and maybe something like 'Spreading misinformation without declaring it as rumors (especially about our game)'.