Hi. I've been doing BST for years. Bring a reusable water bottle with you. The little fold up ones are great as you can stick them in your pocket at the end of the shift so. Although you can stay in the shade most of the time, it can still get hot so stay hydrated, the last thing you want is the headache at the end of the day stopping you from enjoying the evening. And the opposite end of the spectrum a fold up poncho can come in handy! I bring lunch with me as the food is the usual festival prices and you might not get a long enough break to queue for food (although some stalls are helpful if you flash your staff wristband), then I treat myself to something from the stalls at the end. The staff are always great and it's a really enjoyable festival to work at