Lol, I mean a real rule though.
well if you're serious there are a bunch of good candidates...
-Start a new thread when bringing up a new issue, don't start a new topic in an existing thread.
-Links to competing sites are not allowed.
-Try to find the board that is the best place for your topic.
-Perform a search prior to posting a new thread to see if it's already being discussed.
-MLM/Pyramid Scheme discussion is not allowed.
-"Gaming" discussion of credit cards is not allowed.
Especially the last two, depends on how you interpret discussion (for pyramid scheme) and gaming (for credit cards)... you could argue the entire credit card board is about gaming the banks!