Couple of other things to consider...

1. If you are a light sleeper or get disturbed easily by noises around you (i.e. snoring), bring some ear plugs for the overnight.
2. Put your IDs and phone in a ziploc baggie in case it rains when you aren't wearing a jacket. It will also allow you to dump water over your head if it warms up too much without having to worry about damaging your phone.
3. Get to the shower trucks as soon as you can after you get to LaGrange and get some food in you. The longer you wait in the day to get in line, the longer the lines will be.
4. If you are going to get a massage, bring cash, and put your name on the list as early as possible.
5. Get up earlier in the morning than you think you need to. It takes longer than you think to pack up all your gear, get it to a truck to be loaded, get some breakfast, get loaded and ready to go, and then get in line. You don't want to be last in line leaving LaGrange as it can be a very long wait to get started.