USAG Membership Card (or a picture of it on your phone)... and any credentials they may have sent you.
Your coaches gear - Warm ups or whatever it is you coach in. Take an extra set, just in case (We had a younger coach split her leggings, at a practice, while sitting and talking with a group of girls. At a meet, it would have been SOOOOO much more embarrassing... oh, and please wear undergarments

).
Money for parking, if necessary.
Have your phone fully charged... parents might get lost / be running late and may need to contact you!
Writing utensils so you can keep track of POSTED scores.
If possible, in advance, check to see that your girls are in the right age divisions. Nothing sucks more that to get to awards and a girl is in the wrong age group (major drama if she SHOULD have placed in her age group, but didn't in the wrong one - nobody wants that!). If they didn't send anything to verify names and birthdates, take a copy of your roster with names, levels, and birthdates.
I know it's States and the judges SHOULD know the rules, but your copy of the Xcel COP ... with potential questionable things tabbed (cast angle explanation page, split angle explanation page, pages with unusual skills that your gymnasts may use, etc).
They should feed you and provide for thirst quenching, but it never hurts to take water with you!
Make sure your car is good to go. It would suck to break down on the way.
Leave early - you never know how BAD traffic will be.