2a. Due to #1, you will find that there are many days when your band students will be out of your rehearsals while participating in another activity. IMHO those "active students" either can already play their band music or will be able to do so faster than the others. Teach the ones who are in your rehearsal and don't fret over the others. NEVER complain about students being gone for another activity!
2b. Due to #1, DON'T OVERPROGRAM, especially in year one.
3. Be visible at other school activities/events. Your students and their parents will notice and appreciate your support of other organizations and will be ready to step up for you when needed. Good time to brag to band parents about their child. Lays foundation of communication which will come in handy if/when you need parents to help with student discipline issues. BTW: when that happens, open the discussion with something positive about the student. THEN go for the problem and your expectations.
4. Be proactive with your admins and counselors. Get out of the band office and make person to person contact. Don't be a pest, just stop by to say hello, keep it short (they have a lot on their plates) and always take the opportunity to invite those folks to your rehearsals, even if its only for a few minutes in their busy day.
5. On days you eat in the school cafeteria, sit with the coaches. Your students WILL notice.
6. Get to know the bus manager, maintenance staff, secretaries and call them by name. Take the time to acknowledge (and thank them for) their importance to everyday school life. Ask them how you can make their job easier. The secretary likely has a mental list of things your predecessor could have done better. She runs the school, and can/will save your bacon many times even before you know you're in the skillet.