I wrote this for This Is Fake DIY, not sure wether they used it or not. It's a bit too late if you went to Glastonbury but here is some festival advice.
The festival advice I'm sure most bands have given you is that you should smear yourself in sunscreen, bring wet wipes, drink plenty of water and avoid dodgy burger stalls so you don't die of food poisoning. This is because most bands nowadays are a bunch of wet-behind-the-ears, public schoolboy softies.
I don't believe in doing things by halves. If I'm going to a festival I want to fully immerse myself in the experience. To do the same, I suggest that you don't bring anything with you - not even a change of clothes or a tent. Actually, scrub that. You do need to bring one thing with you, and that thing is booze.
You will need this to help you take the harsher edges off of your festival experience. I suggest that you smuggle in a mix of vodka and some sort of soft drink (I find Irn Bru masks the smell of vodka the best), otherwise once you are trapped inside the festival compound they can charge you an exorbitant amount of money for warm beer in a shitty paper cup. You will find it hard to get smashed on that.
I'm totally for immersing myself in the festival experience, and you should do the same. However, a word of warning and my only real festival tip would be to avoid Glastonbury altogether. If it rains, then that fucker is like the last days of the Battle of the Somme. If it's sunny, it will be full of tiny kids running around your feet and people playing the new Adele record loudly from their overly expensive family sized fucking yurt. And no amount of Irn Bru blended with vodka will enable you to enjoy that.