Here are two things I'm going to say that are different from what others have said. There is a right way to say, "Yea, but.." and get away with it. Watch:

Eval: That was a terrible blocking call at the top of the key, two plays ago! The defense went straight up, and all the contact was initiated by the shooter. Ball didn't go in, no call.

You: I see. You saw the defender maintain good position, but I saw ... hm, I see ... so was I in a wrong position? Is that why I saw it wrong? Should I have stepped down to get a better angle?

Eval: No you had good position, but I bet you weren't reffing the defense. You didn't know where his feet were before he left the ground so you didn't know what was straight up.

Now you've learned something. It's not your judgment that was bad it was your focus. If you just nod and say, "Yes, yes" then you're working on the wrong thing.

The other thing I want to say that's a little different, is to go and work for praise and kudos -- for next year. What I mean is, even if you're the worst ref within 100 miles of the place this year, learn a lot, take it home with you, work on it, and then go back next year and listen for these magic words: "you've improved so much in the last year I wouldn't have recognized you." That's the best compliment anyone can give me, and it's really a great feeling. If you hold out for that next year, the criticism this year won't hurt as much.

One more piece of advice: try to get tape. Tape is the best career accelerator you can get. Take it home and have someone else eval your work. Study it. Use it. It's your best friend.

I am in agreement with everything that has been suggested.

Don't forget to control the things that you can control. Use the mechanics that are in the book, be crisp with signals, hustle (don't rush, there is a difference), personal appearance (be fit, don't look tired). If you feel like your rules knowledge is lacking, start strengthening your understanding. When you are at a 'try-out camp' the last thing you want is to be weak in these areas, the clinicians and assignors will sniff out this type of referee early and it is quite possible that you will be left out when it comes time for hiring even if you are a top official in your area. If a situation with a player or coach comes up during a game you are working, recognize it and deal with it. Lastly, STAY IN YOUR PRIMARY, unless it is a god and country that got missed, even then have a patient whistle.

I also recommend being within earshot of the clinician on the floor of your next game, you might hear them say something to the crew or about the crew that will help you when its your turn.

I know it has been said, but if 'yea, but...' is in your vocabulary, put that away and try something like 'I understand/will'

Good luck!

Ooooooo! This is a good one. I should've remembered to say that. Always go to your game early and listen to the observer's comments. You'll pick up extra advice and also may tip you off to some of his/her pet peeves to avoid.

I've got to tell my story on this one...

A few years ago at a camp, I had a most humorous experience. There were two evaluators on the game. They had positioned themselves on opposite baselines. As lead on one end, I was being told to move "this way" to get a better angle. As lead on the other end, I was being told to move "that way" to get a better angle. After a while (several trips down the floor and a few switches later) there was a timeout. One of them spoke to me about why I still kept going to the wrong spot. I then told him that the guy on the other end was contradicting his instructions and I couldn't keep track of which evaluator was watching me on which end of the court. They had quite the laugh out of that one.