Only join one clan,otherwise you end up with divided loyalties,I've been part of the same CoD clan since they started doing clans(Founder),more to the point,what happens if you end up battling a clan that you are a member of?not sure they'd be very forgiving,especially if you win,tbh being in one clan is easier than being in multiple ones,especially during a war,I mean...which clan do you fight for???