Since NOLA.com deleted my comment - here it is! (You know it's good when it's deleted!)

Jazz Fest first timers- Bring tons of cash. That's just for the admission.
If you want food or water, have a friend lug tons more cash.
Scope out a sweet spot near a stage and rope it off with constantine wire. Then prepare your insults for the dirty ugly hippies and wannabe hippies that cut down your constantine wire so they could grab your spot.
Make sure to buy some souvenirs - get ugly crap that you wouldn't want your family to find when you die. It won't be hard to find. Also splurge on a poster - only like $150 for a postcard-size print.
Unless you're really, really, REALLY adventurous, poop before you go.
Even if you are that adventurous, poop before you go. (Seriously)
Bring a dictionary or thesaurus so you can find the words to describe the odor of the people next to you.
Check the schedule ahead of time for which washed-up performers who have nothing to do with Louisiana jazz or heritage are scheduled to play their music badly.
Or - find some friends having a crawfish boil or barbecue, head over there and put on some actually good jazz or Louisiana music to hear. Enjoy your friends air-conditioning. Bring beer or cocktails which will be a twentieth of the price as at Jazz Fest. When it rains, lament how you'll miss the only good entertainment at Jazz Fest, people slipping in the mud. Enjoy.