I agree with the above. Also take a tyre pressure gauge (and pump?) with you, if you are riding there and back. It is generally a good idea to lower the pressures a few psi to help warm the tyres for better grip and account for that warmth. It's been a long time since I did one but we were also told to remove/fold in/cover the mirrors and tape up the headlights - not sure if that's still the rule - but if it is then you'd better have the right Allen key and some gaffer tape.
Get petrol just before you arrive - some tracks don't have any on site, and if they do it's top dollar.
Prep yourself too - good night's kip and a decent breakfast. At the end, stop before you get really tired (you will) and remember that you still have to get home. Readjust your mental speedo as well - after giving it the berries all day, riding home at legal speeds might feel like snails pace until you readjust.
Some people tape up their number plate while on circuit. I think this is because they're worried that their insurance company might find out they were on track - unlikely to be covered - I think it's probably a bit futile but something to consider.
If it rains, you'll probably have the track to yourself but that's the ideal time to gain confidence in the wet. Tracks are grippier than the road and you don't need racing wets unless you're racing, sports touring tyres are fine.
Panto season again. I'm behind you! *voom* Oh no I'm not!