Have an early dinner, like 4ish, and take a nap before the show. Shower and doll up like it's a new day, have a light meal with lots of fruits and veggies and drink some Gatorade (especially if you're gonna be drunk or otherwise inebriated, stay hydrated, bestie).
To add, if you’re not drinking, take a pain med (Tylenol, neurofen, etc) before as well, to help your old ass bones and joints to not be sore. I usually start hydrating heavy a day or two before. I usually graban Organika or other electrolyte powder instead of Gatorade, and grab a b12 and Coq12. Oh and comfy shoes! Nothing worse than being at like a second or third day of a festival, unable to stand because of sore feets!
Electrolytes are what's important, yeah. I personally take Brode electrolyte multivitamins whenever I'm "going hard", but it's easier to recommend people to grab a Gatorade.
I just saw yesterday that one of my favorite bands is playing nearby this summer with a 3PM start time!
Then I saw there are 6 bands in the lineup and they don't even tell me what order they are playing in. I don't want to watch 6 bands in a row, 2 or 3 is plenty, then let me go to bed at a reasonable hour.
I always inquire what time the headliners are playing at and waltz in after the opening act is done. Except for when Jesus and Mary Chain were inexplicably the opening act with Psychedelic Furs as headliner. Anyways, that was awesome heading home by 8:30 I think.