As for settings, I use shutter priority when shooting motorsport, and sometimes full manual. It depends on the shot you want though... For panning, between 1/80 and 1/160 depending on light levels and to 'freeze' the action as fast as the light will allow.
Use Servo AF for focusing which will focus as you track and as the subject moves. The 7D should be very good for this!
1/80 - 1/160 sec would have to be a slow corner, you do realise how fast these cars will go. Personally wouldn't recommend those shutter speeds especially for panning......
Ok this will depend on the light conditions and which part of the track your able to photograph, it you don't have a media pass, you'll have to contend with safety barriers and fences, so a long zoom is required, but for panning or standard shot, start with the rule of thumb, 300mm lens = 1/320 sec * 1.6 for the crop factor, so say 1/400 sec and that will give you a reasonable shutter speed to start with, once you have mastered and are please with the results, slow the shutter speed down, but remember this will increase the chances of soft or blurred images.
I've see a large number of togs who think they can get decent shots at 1/80 sec and personally most of those imaged would have been deleted on my camera. It takes a lot of practice and a very smooth panning technique to get constantly sharp (printable A3 / A2) shots at shutter speeds of 1/160 sec or lower, especially for bikes and F1 cars.
OJ right it saying shutter priority for some shots, but say you at the top of a long straight, car slowing down, personally I would use AV (aperture priority) and set a smaller aperture (f8) to get car all the car in focus or large aperture (f2.8) to create Bokeh depending on your lens.
You also need to take into account where the sun is, you want it behind you or to the side, reason, detail in the image, you don't want a lot of shadow in your images, just change you position.
Use AI Servo, continuous shooting (but don't machine gun the shot to death), take 2 or 3 image burst and remember to pick up the subject early and keep it in focus before taking your shots whether you intend to pan with the motion or capture it head on and use TV (shutter priority) or AV (aperture priority) depending on the shot.
What lens are you intending to use?