Which track are you going to Dan?
I'd been on a few track driving experiences, before I took my own car on circuit - difference is night & day! I've driven Cadwell, Bedford Autodrome, Donington (short & GP circuit). Have been round Silverstone & Thruxton on experience days too..., I thin either Cadwell or Donington are the best circuit I have driven.
My main recommendation is - book tuition! No matter what lines you think are right, or are driving, they will be wrong! A pro can show you a faster line through corners than you think is possible.
Only other tips are as others have said - relax, don't be tempted to race anyone - there's some hardcore stuff at trackdays nowadays - there was a full on Clio Trophy V6 Cup car at my last day
. Make sure you take oil, check your tyre pressures, etc.
Make sure you warm the car up and down - don't clamp the handbrake on in the pits after going full bore round - in worse cases it could cause the discs to warp.
Another observation of mine is - don't be too keen to get on track - let others get it out of their system. I've always noticed it - people seem to go mad as soon as the track goes live - far better to sit on the pit wall, watch people go round and then slot in when the track activity has settled a bit.
Having said that - assuming you are on a track-day with open pit lane rather than sessions?
All said - you'll have a great time!