1. I typically use panning, but as mentioned, there are MANY techniques that you can use.
2. I try to shoot as level with the track as possible, sometimes even on my stomach. I only use a tripod if I want to duplicate a specific shot such as "the line" through an S corner, or if there is a good battle going on and the two cars are always close in the same corner.
3. Yes, the blur is created by using a lower exposure and panning with the car.
4. I typically focus very tight on the car (300mm lens) to avoid having to crop the photo later.
5. I have not shot indoors as of yet, but I would probably start with an ISO of about 200 or so and experiment with fill flash. Maybe bump up the ISO depending on the lighting conditions.
6. There are some great tips here in this thread that I have yet to try. I would suggest looking at exif data for some of the pictures that you find. this can give you a pretty good reference to start with.

Hope that helps