My advice is expect to make mistakes.
I used to go into games expecting perfection and when I made one mistake I was thrown off. As some will tell you no one has called a perfect game so you can't expect yourself to either. After you MAKE your first mistake say to yourself "I'll talk to my partners about that play later but now I have to concentrate on the next play". Then you must follow through and forget about the mistake because if you harp on it then you will make another mistake.
I had some great advice from my R in one of my first college games. He said call the obvious in your area and don't worry about ANYTHING else. It simplified my thought process and allowed me to call a better game. Your partners should help cover anything big that you might miss.
My first HS Varsity game was a packed house (over 2,000) and it was 2 very good teams. I would have been nervous but I had a cold and was feeling pretty sick. It helped take my mind off the moment because I was thinking of how lousy I was feeling. I was praised highly by my R after the game and was given almost a complete varsity schedule after that. So my advice to you would be to catch a cold a couple of days before the game
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