1. Nothing that you did in high school means anything anymore.
This isn't to say that you can't reminisce on great things that happened to you in the past. You can. You should. You've worked hard to get to this point, but so did a majority of those around you. People have little to know knowledge of who you are (Especially if you're out of state), so assume you're at the bottom now, because class wise, you are. You will probably be on a lower part, and that's okay. It doesn't mean that you're a bad person. This isn't to say that you can't work your way up the ladder, but it's likely been awhile since you've been at this place on the totem pole, so just don't let it freak you out.
2. Don't sweat the small stuff.
This applies mainly to marching, but it's applicable to a lot of areas in college band. If you come from a competitive marching program or a drum corps, college marching band may seem like a bit of a joke. It's incredibly laid back, and if you are used to high intensity jazz runs and copious amounts of visuals, it may seem elementary. However, keep in mind that these shows aren't like the ones you did in high school. They're designed to entertain the average Joe, so just relax and have fun with it. It's only as enjoyable as you make it.
3. Take Care of Yourself
Your schedule hour wise is likely just as busy as it was in high school. However, your schedule is much more dispersed. With these crazy hours, It's easy to forget to eat a meal or drink water. Set a reminder in your phone, write it on your arm, something. Your ensemble will thank you. You'll be better focused and less likely to run into people.
4. Don't be a Stickler About Technique
This is included because depending on your prior experience, the style of marching will be vastly different from what you're used to. In my own experience, I've marched in a contemporary style for the last five seasons of my life. When I first got to camp, the style in which my university marched was more militaristic than I'd been used to in the past. While a part of me wanted to vehemently protest by marching the way that I was used to, I soon realized that this style best fits the laid-back jovial style in which we played. Be willing to change.
5. Learn to Say “Screw It”
College is already stressful enough with classes and move-ins and textbooks and... I'm getting stressed just thinking about it. The point I'm trying to make it that not everything that you play is going to be perfect. You're going to chip notes and miss direction changes. Don't worry about it. Fix it, duh, but this isn't something to lose sleep over. If you don't have time, you don't have time. Keep focused in rehearsal and fix stuff on the fly. If you find down time, hammer out the parts that sound like garbage. Chill and it'll all work out. You aren't getting scored as an ensemble on this performance, so just play well and enjoy it.