The gaming convention is open forum. You can either show up and play at one of the open tables or play in the A&A tournament. The open tables are first come, first serve. Usually the guy who hosts the A&A tournaments reserves a few extra tables in the back of the convention room for players who don't want to play in the A&A tournament but just want to play a game. As A&A requires a lot of table space, it is best to get there early. The convention hall has capacity for a lot tables but there are hundreds of players who attend, playing all kinds of different games. So there is a limited number of tables reserved for A&A. Both the A&A tournament and free play. Most of the time my friend and I go to just play a good game of Global 1940, Alpha 2 or Alpha 3. It's a great way to meet new players and provides plenty of table space and room for a large game like A&A. We don't play in the tournament usually. The reason being is, the tournament requires that you play a game on Saturday, then the winners from Saturday square off on Sunday. That works if you're playing Anniversary but Global requires more time. So we usually start playing Friday night or Saturday morning through Sunday night until we can't play anymore.
The A&A tournament starts on Saturday mornings at 9AM and goes through Sunday evening. Not sure what the default game is. Used to be Anniversay edition but I believe they changed it to either Europe 1940 or Pacific 1940 in the first round and Global 1940 for the final round on Sunday.