I like shooting both raw (easier to play with colors, clarity, and adjust) and jpg (quicker for getting pics up somewhere) but the combo can eat through memory cards like Pacman. I carry a handful of 32MB cards with some 16MB and 8MB spares because the last thing you want is to run out of space and have to start deleting photos from the viewfinder in the midst of the final round. I also carry a space battery and recharge everything at night in case.
A good lens can also empty the wallet. Three lenses that will provide a good range for covering almost everything are a telephoto (mine: Canon 70-200mm, f/2.8) to capture track events, a midrange zoom one for pits, shots of drivers and the crew and car shows (Tamron 28-75, f/2.8), and a wide angle (Canon 10-22mm, f/3.5-4.5) that offers excellent close-ups of products, decimated race cars, and engine bays. Keeping the equipment clean is a must. There’s so much sand, gravel, smoke, and dust you’re exposed to capturing track photos that can create spots on your photos that make you wonder why it's snowing in Texas in July.
The most important thing on track is to not be an asshat. Obey the track marshalls, corner workers, and emergency workers. Stay out of the way of teams and drivers. Never, ever, ever lay down on the track. Common sense, right? But one photographer at Road Atlanta learned his lesson the hard way and it's hard to take photos in a full body cast. Behind the camera, we sometimes disassociate ourselves from the activity on the track but there’s also a level of responsibility required. You have to put down the camera if you can help. At FD Wall, Joon Maeng's car caught fire and I watched a nearby photographer reach for a nearby fire extinguisher rather than continuing to take photos. Props on using your noggin'!
And then there's the weather. Rain and offroading excursions are one thing but you also have to cope with the sun. Sunscreen, a good hat, sunglasses, lightweight light-colored clothes including pants on track, and close toed shoes are a must. A bandana applied over the mouth helps keep from inhaling clouds of tire smoke and you get to play dress up- cowboy or bank robber? Typically, I'll carry my telephoto and camera body on a strap (Black Rabid Cargo RS-5 which has a few pockets for business cards, cash, and ID) and put 3-4 waters and a granola bar in my backpack since it's often 2-3 hours in the high noon sun shooting a practice or qualifying session.