I've always been of the school of thought that it is the responsibility of the person paddling out to take one on the head in order to stay out of the way of the guy that's dropping in. Usually it's going to be pretty obvious which way the guy intends to go. It's the paddleouters (yes, I just made that word up) duty to paddle towards the peak, not the shoulder so he or she doesn't disturb the ride. If that means you get axed in the head, you get axed in the head. Additionally, do NOT ditch your board in this circumstance. Duck dive and hope for the best. If you don't know how, learn.