Slant your take off and drop in over their shoulder if you can. A lot of people seem to think that they can spin and get in front of you when you are already paddling and committed. I try my hardest to keep this from happening via an the "angled right-over-their shoulder" drop in; they usually eat it. I've had couple people get mad at me for doing this, but I remind them of their behavior and they usually shut up and paddle away.

That said, I have been burned and it will happen again. Just too crowded sometimes. Last Saturday, a guy dropped in on me and when I said "hey", he fell and shot his board right at me. I didn't need to say a thing to him though because his buddies ripped him a new one for it. I just laughed and went back to my line-up spot.