Okay, I have yet to put up any rules, so here are some.
Rule one) NOTHING from another anime or manga unless the character is somehow related (i.e. looks like a character, has animalistic properties, etc.)
Rule two) Have at least ONE OC of your own creation. Trust me, you will want it later.
Rule three) Don't criticize someone's work. If you have something bad to say, find something good.