Battery hold down - make sure it is tight
Floor mats removed
All loose objects removed from car - cockpit & trunk. (This means anything that isn't bolted down.) Bring a box that you can throw everything in when you empty the car. If not, your radar detector, tapes, etc. will be scattered, run over, etc.
If you have a nose mask (bra) for the car, put it on. You won't believe what flies through the air when you're on the track.
Put on metal valve caps. The plastic ones can fly off or take them off al together.
Use tape weights inside the rims, not clip on weights which can fly off.
Remove wheel covers. They can also come off.
Rain-X your windshield if it looks like rain.
Use Z or better rated tires and make sure they are in good condition! This is the most common cause of failure during extended high speed runs, and when a tire goes, control is lost. Typically it is recommended that you put 300-400 miles on the tires before taking them to the track (assuming you're not using shaved tires). Also, a new tire with full depth tread blocks WILL feel more squirmy than worn or shaved tires.
Things to Bring:

For You:

Clothing-Cotton is best. Cotton long-sleeved shirt or jacket is better than any synthetic (fire).
Shorts, T-shirts etc. for non-driving sessions
Wear comfortable sneaker-type flat soled non-slip shoes and socks. NO SANDALS. NO HIGH HEELS. NO BOOTS.
Bring a ground cloth or some garbage bags to put things on/in. The paddock may not be fully paved, which can mean mud if it rains
Rain gear - rainsuits, umbrellas, boots, change of clothes. If it is raining and you get wet changing pads, etc. then dry clothes and shoes are REALLY nice. A big tarp is handy too.
Gloves
Sunscreen lotion, a hat, sunglasses, bug spray
A fire suit, five point harness, and helmet can ease your mind. Some or all of these items are required at some events
Pens and pad for notes
Camera and film
Aspirin, acetaminophen, or ibuprofen
Maps
Coveralls
Overnight kit
Membership cards, Check books, credit cards, cash, license
Cooler
Earplugs
Snacks
Folding chair

For The Car:


Duct tape
Air pressure gauge and air compressor.
If possible, an air tank. There may only be air hose and there is often a line
Torque wrench
Jack
Extra brake pads (front and rear) and tools for changing brake pads.
Window cleaner and paper towels
Shock adjustment tools (if you have adjustable shocks)
Full fuel can. Gas may be available at the track, but often only for part of the day. It may also be racing fuel and cost several times more then regular gas. It is not unusual to go through a full tank of gas during the day
Brake fluid
Engine Oil
Brake bleeding gear
Service manual
Tires

Originally posted by Fritz Flynn
If you drive an fd bring a spare one along

Originally posted by cpa7man
Ha, Most of us only have one, not like you. What is it 3 or 4?

You really do need to tow the FD to the track, that way you can get home.

Originally posted by Fritz Flynn
I do tow and thank God for my truck and trailer. I'm going to vir this weekend to play around in freezing rain and snow