Oh, I forgot! This is a list of things I think you absolutely must bring to a music festival. I think I'll start doing a 'Packing 101' feature, like for beach stays, city stays, etc. If you have any ideas for more packing 101's, leave it in the comments! (:
-Backpack: This should be a good, high-quality, very durable backpack. It'd be best if it were waterproof, but if you can't get your hands on one of those, any decent-grade backpack will do. Make sure it has pretty well-cushioned shoulder pads, though, or your shoulders will be killing you while you rock out to The Killers! I recommend Herschel co., or honestly, I love Speedo Pro backpacks... they're huge and waterproof, and stand up to pretty much everything. They come in tons of colors too!
-Bug Spray: This is a given... but if you haven't heard of it yet, also try the Bug-Band. It repels bugs for up to 120 hours, and comes in tons of colors, even glow-in-the-dark! They have a pretty strong smell, but it's not unpleasant.
-Sunscreen: This is also a given! I'd recommend SPF 50 or greater. Make sure it's something easy to apply and re-apply, like a sport spray. I'd definitely recommend a spray.
-Hat: Like I said in my previous post, though... a smaller hat is better than a large hat. Also, make sure this is pretty cheap. You don't want to spend lots of money on something you're probably going to lose.
-Extra pair of comfy shoes: Your feet will be killing you if you wear heels... pack an extra pair of shoes just in case! Make sure they're pretty compact, like flip flops, so you can just throw them in your bag.
-Cash: It's just a lot easier to bring cash, most festivals don't support credit cards.
-IF any of the bands are doing meet & greets: something to get signed! You don't want to have to pay for a shirt for them to sign if you already have their album or something like that, do you?
-Walkie-Talkie: Since your cell coverage is probably going to be spotty at best, it'd be wise to bring a walkie-talkie so you can communicate with your friends.
-Waterproof blanket/ poncho: If you don't plan on getting right up in the mosh pit and just want to sit and relax to music, make sure to bring a waterproof mat/ blanket. A big rain poncho will also do just fine to work double duty.
-Toilet paper or babywipes: I don't even need to explain how dirty and gross port-o-johns can get, do I?
Of course, this list doesn't cover those who camp at their festivals. I didn't get the opportunity to camp out at Firefly, but if there's anything you feel I forgot, don't hesitate to add anything in the comments! Thanks!