I was a senior instructor with Easy Track before they went belly up last year. Some of this has probably already mentioned but I'll say it anyway. Make sure you drink plenty of fluids and keep hydrated. If you can, see if an instructor can take you out for a few laps . They are there to help so use them. You have all day so take your time to get up to speed. The Main thing to do is relax, keep berthing during the sessions (it's easy to forget this and actually end up holding your breath for most or the lap lol) At lunch don't fill up with stodgy foods (chips, bad carbs, they will make you feel sleepy and lethargic) try and eat light with food packed with natural sugars. If you need help at any point, don't feel afraid to ask anyone. They are there to help. Don't feel under pressure or intimidated by others on super trick track bikes. Just concentrate on what your doing, not what others are doing around you and you'll be fine. Most of all enjoy it. You are going to love it
In my view, track riding is very different to road riding. One of the reasons people are fast is because they do a lot of it. If you haven't, it's not unreasonable to assume that you won't be anything like as fast because you haven't had the practice. It's just like anything else. You can spend 20 years on the road and you won't instantly be as fast as some 16 year old who has only ridden on the track but has been doing it regularly for the past 5 years on one form of two wheeled transport or another. Why do you think the kids on GP3s are so fast? Track is fun when you only really try to beat yourself. But boy, do you learn a lot in a short space of time.
You'll probably tell me my technique is all wrong, but here we go. Can't believe how much I enjoyed it!