How exactly does the first round work?
You'll need to fill 4 bottles for your entry (do more while you're at it so you can enter other competitions).
For the first round, you only send 1, but you need to hold on to the other 3 in case your beer goes to the 2nd round. You are allowed to re-brew for the 2nd round, but that only really works with session-type ales.
At the 1st round judging, each entry will be judged by at least 2 judges, and there's usually a flight for just about every major style category. Some of the bigger sub-styles (American Pale for example) are usually split into several flights and the best of those beers go to a mini-BOS round where 1,2, and 3 are selected. There's been a lot of grumbling by some folks about the mini BOS concept, but it's probably the sanest way to go about selecting the 3 best beers out of 40.
This year, the "queued judging" format will also be used more extensively for the large categories. In the past, all of the entries were split into flights by the coordinator and assigned to a panel of judges before the competition. In queued judging, all of the beers would be lined up and each judge panel goes and selects the next beer in the queue. When they're finished with a beer, they go back and get the next beer. I've heard that it works pretty well. All this depends, of course, on the regional competition coordinators.
Anyway, get your brewing schedule figured out and good luck!