The rules are simple:
1) Don't be abusive to the other members of the board
2) Don't post porn.
I don't personally care about the porn, but the ISP that hosts this server has a "no porn" policy, so therefore I have to as well if I don't want to get in trouble. Plus, that is just not really the point of this board.
If your posts are useless and/or offensive, especially towards a specific member of the board, then they will very likely be deleted and you risk being banned as a member.
That's it, the rest is easy - post interesting and quality stuff and keep it on topic to the board that you are on - unless it is the chat board and then you can do pretty much anything you want.