1. Just keep breathing
2. Be flexible
3. Drink water, lots of it
4. Plan more than you need but know and accept that you won't get to all of it
5. Go with the flow
6. Be ready to nip kid misbehavior in the bud because they are testing your boundaries from the very beginning
7. Be organized and ready to go with materials that you need laid out and easy to grab
8. Have your first few days schedule written out to nearly the exact minute with time spent on each activity clearly designated
9. Plan activities that keep kids busy and out of trouble while you take care of first day paperwork like really long attendance sheets and the lists of who is walking, who is bussing, and a myriad of other forms you have to deal with at the beginning.
10. Plan less-threatening activities, like don't require kids to do a lot of sharing, because they are nervous about their first day
11. Any materials you are not going to use, put them away out of sight so you don't feel overwhelmed
12. Even if you don't know how or what or why of things, act like you do
13. Give the kids a fresh start every year. It is helpful to know the red flag behavior problems and what other teachers have done to manage them, but that is it. And tell the kids it is a fresh start for them. Don't ask them about last year, ask them to think about what kind of student they want to be this year and start there, with what they want to achieve themselves in the 5th grade.