Show up for the game on time, meaning at least 30 minutes prior to game time. Use the time to properly prepare to do the game including a good pregame with your partner.
Develop good timing on calls. Good timing = not too fast. It ain't nothing till you call it so make sure you saw what you think you saw and then call it. Never call a pitch until after it has hit the catcher's mitt, and never call a out on the bases until you know the fielder did not drop the ball.
Never make a call "on the move". Get set and make the call from a stationery position. Also, don't get too close to a play.
Study the rules for whatever level of ball you will be calling and learn as much as you can, but make sure you know the right answer for the MYTHS.
http://eteamz.active.com/baseball/ru...ths/index.cfm?
Have fun, don't be uptight.