When I did district and all-state music festivals back in my middle and high school years, I was never entirely sure what I was being judged on during my audition. I knew what scales they wanted to me play and what piece they expected to hear from me, but I had no idea what things they were listening for within those requirements.
Unbeknownst to me at the time, you can look online at the evaluation sheets that the adjudicators use to score auditions. They're public knowledge, but I had no idea when I was young and shaking in my boots at the thought of someone taking notes about me while I played.
So in the spirit of making things easier for the next generation, here's a list of where you can find evaluation sheets for all the different district festivals in Massachusetts. If you're not sure which district or festival applies to you, your band teacher should be able to guide you to the correct one, and if you live in another state, you can most likely find a similar offering on your own state's district website.
Eastern District Senior Festival
Eastern District Junior Festival
Central District Senior Festival
Central District Junior Festival
Western District Senior Festival
Western District Junior Festival
Northeastern District Senior Festival
Northeastern District Junior Festival
Southeastern District Senior Festival
Southeastern District Junior Festival
Once you know exactly what you'll be graded on, take advantage of that knowledge to direct your practicing! Print out a bunch of copies of the evaluation sheet for your festival and keep them handy in your band folder. At least once a week, record yourself playing the audition piece, then listen back and grade yourself using the sheet. Use the areas that are the weakest as jumping-off points for your practice that week. Good luck and happy audition prepping!