Double Teaming

Can you please clarify the rule (if any on double teaming/triple teaming, etc..) within and outside of the 8 m and 12 m?  Is there any rule?  If so, what is it?  How does this rule relate to girls needing to all be marking up a player.  Does a triple team count b/c they are all marking the same player?  Any clarification you can provide would be greatly appreciated.