Ultimately you want to drive your 911 to the track, enjoy your time on the track and drive her home again.  Here are some tips help make sure this happens:

Before you go to the track

Check all fluids
Check wheel nut torques.
check tyre conditions.  They are going to be tested round the track so good condition is essential.
remove the spare.  Its a space saver and you wont be using it around the track
check tyre pressure and make a note of the readings
replace the brake fluid.  Top up if necessary and replace if not done recently
check the thickness of brake pads and replace if within a few millimiters.  Your brakes will get a real hammering on a track day so this is a real must do.
collect some basic tools together. wheel brace, jack, axle stand, commonly used spanners and screw dirvers etc.

Spare Parts to take with you

brake fluid of choice
complete set of brake pads
engine oil

Clothing

crash helmet
banaclava.  These are generally fire proof, but also make donning the helmet easier.
race shoes.  Not essential.  thin soled trainers will provide some reasonable peddle feel.
race overalls.  These do provide fire protection, but is not worn by all.

Post initial speed laps

having run your 911 for a few laps at decent speeds:

check the tyre pressures.  They will have increased, so adjust as necessary.
check fluid levels.
check wheel nut torque settings.

I often find even after torquing the wheel nuts before the 1st session when I check them hot after the first time out they can come slightly loose (a quarter to half of a turn at the rear is usual)
Re-torque them hot after the first session and they dont move again, though it is good practise on track to check them before every session!!

In a 911 with the dry sump oil system make sure for track work to only fill the tank to half way between the upper and lower dipstick marks.
Overfilling the oil just results in venting oil into the breather system

Tbh I wouldn't be too precious about removing the spare wheel, with the standard weight distribution in a 911 being 60% rear, it doesnt hurt to run a bit of ballast up front. Likewise running a bit more fuel can help with the 911s natural tendency to understeer