Just to add on to what the others have said:

Although this isn't car specific.

.

.

I'd say be more observant than ever on track.

Of course it depends what kind of people are on the track when you're out there but keep an eye on the mirrors when you can.

Prior to the trackday itself, change the brake fluid to something that'll cope a bit better:
Motul RBF 600 or 660 is what I prefer.
http://www.opieoils.co.uk/p-894-motul-r ... fluid.aspx
http://www.opieoils.co.uk/p-1078-motul- ... fluid.aspx

(I think a couple of bottles will leave you with some topping up when required

- not sure, as I just bought about 8 bottles in one go

).

Remember when coming back into the pits

-
DONT PUT THE HAND BRAKE ON
!

Leave it in gear, and always start the car with the clutch fully pressed down

(I do that all of the time anyway better for the car).

For noise, it depends where you are, some places sound test you before going out, so make sure when they do, you've really run the car for a while.

'Loud' days are typically 105db, my one is 104.9 decatted, so you'll probably be ok.

(ask the organisers what it is on your day specifically)
If you live near the track, go down on another track day and ask if they can test it quickly as you have one booked.

Or if you really want to test it, you could get a device from maplin but it's not going to be the same as their kit, so bare that in mind.

Obviously this depends on your driving but it's
possibly
worth changing the gearbox oil afterwards, it's not a necessity but I've seen some good enough reasons to do it.

(maybe not after 1 day but a couple)

Which track are you heading to

?