The transition from backswing to downswing is where amateurs make the most mistakes, usually because they're thinking about what to do instead of just doing it. My move at the top is simple, so it's easy to repeat without having to think about it.
Hips Lead, Arms Drop
I use my shoulders on my backswing to power the club back. Once I get to the top, however, my lower body takes over. Notice how my belt buckle and the Puma logo on my pants are slightly hidden in the first photo, but that you can plainly see both in the second.
Also notice that everything from the waist up has remained the same (the Puma graphic on my shirt below the collar hasn't moved). I've turned hard with my hips and left everything else behind.