tnluong,
A couple of things to think about for your first game.
1. You will feel a little overwhelmed at first, you'll get in the groove soon. If everything seems to be happening too fast, take a couple of steps back. Get a wider angle and you'll be able to see better. Especially on the baseline.
2. Focus on the defense. If there is contact
and the defender did not have a legal guarding position
or he initiated the contact (by moving toward/into the offender, sticking a leg/hip into his path, swinging an arm down, etc.), it's a foul on the defense. Otherwise it's either an offensive foul or nothing. The key is the defender.
3. Once that whistle blows, slow down. Take your time reporting fouls to the table. Make sure your partner is ready before putting the ball in play. It will calm you, give you time to think, and make you look like you know what you're doing.
4. You don't hear it on TV or from the stands, but good referees talk a lot. Talk to your partner, the players, the table. Talk to the coaches (just not very much
) The game runs a lot smoother when everybody knows what's going on, tell them.
5. Have some fun.
BTW, your partner is the only one who needs to know it's your first game.