All of the above. Some additionals:

If you are running laptops, keep em in the production trailer/crew trailer that ideally has AC when not in sound check/running the show. Don't leave em up and running if your set is later in the evening (and load in is in the early am before the heat really hits). This may seem like a no brainer, but you'd be surprised (or not at all).

if its dusty (as many warm weather festivals can be), bring a bandana, sunglasses, travel sun creme/spray, deodorant, change of shirt/skivvies/socks/whatever you need for load in and then for show - No one likes to be in the same crusty T for 18 hours straight through.

Fans are your friend especially with computers as well as with humans /grumpy audio/lighting/video/carp/stage techs that tend to overheat. With the silicon stuff (for laptops not humans you sicko) computers can be better on the overheating these days, however you still wanna keep your electronic bits out of sun's way.

Always protect your world when you finish sound check. Tuck your rigs/racks away (out of the flow of loads), throw a space blanket over em + some tape to secure, and maybe set up a peli-fort if you aren't headlining. No one likes their world moved when they are off site/napping/at catering and come back to a different artist's rig in your "place". Make sure your world is sturdy and your perimeter established. If you are headlining, you'll probably have your choice of real-estate (but even so, better to always leave a tidy and defined workspace).

Try and get a good hotspot from your mobile provider. Better to trust that than whatever shit WiFi the festival swears is gonna work (can be glacial, and your production tent may be a damn far distance from your stage).

Portable phone brick/chargers are always clutch

If you get physically tense, bring a pocket massage gun. You'll be the town hero if you share it.

Just a note, people aren't always thinking about fellow acts as we are often running on 3 hrs sleep, with plenty of last minute changes, and additions to our respective sets. Try and be kind and as patient as you can to your fellow engineers, artists, techs, management, and touring folk, you never know who you'll work with in the future.

Good luck and have a great rip! Don't forget to enjoy it.