Get a steady stance on nice firm ground (you dont want to loose your footing half way through a pan!)
legs aproximately shoulder width apart, tuck your arms into your body to help support the weight of the camera
start to track the car nice and early with your feet facing the place when you want to take the photo and twist with your upper body, when the car fills approx 90% of the frame gently sqeeze the shutter and continue to follow the car well after pressing the shutter to avoid jerky movements
stick it in shutter priority and leave iso on auto, you dont want to be trying to adjust too much information, especially on your first go
start of with a relatively fast shutter (if you want some keepers for the end of the day) then slowly bring the shutter speed down when you gain some confidence, presuming its cars your photographing, start out at say 1/400th of a second, that should get you some nice sharp images if thats all your interested in, then as you gain more confidence that shutter speed will come down and before you know it you'll be on 1/100th, 1/40th and you'll be getting some really lovely shots with good wheel motion and background blur whilst still keeping the car nice and sharp
if you've got time before your going, go and sit at the side of a main road (keep yourself safe though) and practice on passing cars, you'll get a few funny looks but atleast you'll get some practice in before you attempt it on cars that are going flat out
and most of all, enjoy yourself, move around the track and eat some greasy burgers

your not there to pay your mortgage so dont be disheartened if you end up with a memory card full of rubbish, we all start somewhere
out of interest what equipment have you got?