Ive been doing this sort of work for around 7 yrs. Its very seasonal and can be very rewarding. I once worked the pit at V Fest with the Kings of Leon lead singer dripping sweat on me. Good in some ways, bad in others lol.
You get used to the hours and its in short bursts, a week here, a week there then 3 weeks off.
You can earn good money in the Summer if you find you like it. The Olympics however is a totally different beasty.
High profile and exhausting but the rewards will be great. In your 12 hr shift you will get breaks for lunch and tea breaks etc. You will need to be ready to be working for a good few hours though. Sturdy footwear, tape your feet up if you get blisters.
Plenty of water.
Dont bring bags etc to the venues as there is no guarantee you can keep your stuff anywhere and you do not want to risk things getting stolen.
After all that, just enjoy and I hope to see some of your there