Have your scores ready to go a couple of days before the contest. I like to make folders for each judge.
Bring originals with you to contest.
Medical releases info for your students.
If you are feeding your students, make arrangements well in advance, and always check every day for a couple of days in advance.
Bring extra set up charts.
When on stage, don't rush, make sure the band is setup as close as possible to what you want. The judges will wait, they have been through this also.
No matter what happens, stay up beat and positive.;
Bring extra of everything.
Double check your percussion equip, mallets, sticks, music, pants, lol.
Reeds, mutes, double check everything.
Hope this helps