[scottk_61]

Having been to more than a few Nationals, here is my advice.
Make contact with some of the other umpires beforehand
Be early for everything.
Be ready for everything.
Have your gear ready and then check it again then when you think you have everything packed, check it again.
Go with a attitude of having a very good time and looking for some good ball.
LISTEN TO YOUR UIC, even if at first you might disagree at first.
In the umpires meeting listen to all that is said even though you might think you already know the answer.
Have some nice dress clothes ready for the coaches and umpires meeting, your UIC should tell you what is expected ahead of time.
Don't show up in shorts and sandals!! I personally suggest that you not wear cutoffs at anytime during your stay at the tournament, even at the hotel.
Clean and neat is the idea.
Remember you were chosen for a reason and this is your chance to show your skills.
Don't think that maybe the tournament is beneath you.
I was once selcted to work a 10U Girls National after having gone to an 18A and the Women's Open SP which had followed the Armed Forces Championship.
Working down in level does indeed lead to better things, they might need you as a leader, be ready to lead if called upon.

I got my start in NCAA ball after having been seen by a D1 coach at a girls SP tournament.
People will notice you.

When a coach comes out to ask a question, LISTEN to them and get together with your partner(s). Make that decision as a group and let the appropriate ump make the call.

Finally, have a good time

Have a good time
Have a good time
Have a good time repeat as necessary.

Just as a final note, treat the players to the best game you can give, just like you want to have.

Oh yeah, HAVE A GOOD TIME.