I know several USBL guys including the Supervisor of Officials, Tom Palmgren. I would love to work the league, but
since I'm out West, no dice. The CBA is coming out west next year, so I will work then.
I will second what BBarnaky says about rules knowledge to an extent. Coaches and players know the rules better than most High School and College coaches, but still THINK they know them better than they actually do.
Anytime there is a restricted area play, the player charged with the foul always points to the floor. Either in or out.
Defensive three seconds, ball going over the corner of the backboard being a live ball.(to be out of play it must go squarely over the middle portion of the board).
Also learn and use "pro" terminology. It's the "restricted area" not "no-charge zone." Offensive foul applies to anyone on the offensive team, not just the player with the ball. Flagrant fouls (penalty 1 and 2). Clear path to the basket fouls, away from the play fouls etc. That having been said, don't go into the tryout thinking you have to be perfect. That's not expected. Just be the best you can be and work hard. (advice given to me a couple years ago by Ronnie Garretson.)If you're good enough, they'll see it.
Good luck! Let us know how it goes.
One other thing. Before you go, work very hard on your clock awareness. If you can show that to be a strong part of your game, that will make you stick out from the others!