a couple things I forgot.. bring a portable fan for your tent. I can't stress enough how fugging HOT it is another amazing thing to have is a spray bottle that has a fan on it. they're cheap, and you can mist yourself down when you get too hot. also good for misting others, they will be eternally grateful + you could meet some cool people
yea, water and shade are the most important things to bring IMO. chairs, blankets, extra shoes, cigarettes if you are a smoker. if it rains a tarp will probably come in handy and are a good thing to have around anyway. pretty easy to string them up on a vehicle and have a little lean-to for some shade. also if it rains, it's muddy as fuck. the roads anyway, concert areas are usually okay.