I was going to post this as a new topic, considering your questions were specific, I may as well tack on the end. I will answer your questions as to what I do and think about when covering an event (others may not agree and have different views, I am comfortable in what I do though, I like my results, as do my customers...so here goes)
If I am at a new track or dont know it too well, I will do a track walk, really take a good look around and see where potential action hot spots will be. Take some test shots, see what focal distances will have disturbing backgrounds, the path of the sun throughout the day, burroughs or lower areas i can shoot from, where will be a good area to pan from, where will be my safe spots trackside for face shots..things like this.
Once the riders are in warm up laps, I will usually watch for the first lap or two. Paying attention to what will provide action, what the line seems to be for most, what level of rider can clear what jumps, doubles, triples, etc.
My technical setup. The examples I am posting were shot with a Canon 70-200 2.8IS, on a Canon 40D, 8GB card. I didnt need IS on this day, thats just one of the lens' I have.
I always shoot in RAW. I have complete control in my editing. All the below images have some editing (not too much). I hear complaints about RAW takes too much memory, BUY MORE CARDS THEN!
1. I was down below the rider on a high berm.
ISO 100 f5 1/1250. I took a 4 sequence burst and this was the best shot.
2. This corner offered a ton of action. The bikes basically came to a stop, with the dirt drying out and riders piling up on eachother, many shots were captured here.
ISO 100 f4.5 1/800. 2 sequence burst
3. Just keep moving around the track to all the hot spots you notice, a shot will sooner present itself more than later.
ISO 100 f3.5 1/800
Emotion is everything in sports. No matter what sport it is, you need to see the face. Sporting images will show face 9 out of 10 shots. Kids in sports will always attract sales to the parents. Capture both the kid and the look, it's all green!
4. ISO 100 f5.6 1/640
PANNING. This doesn't come easy to anybody. Practice is all I can say. This shot, I had the 70-200 on. I was approximately 100' from subject. The riders were coming from a high speed left hand corner.
Settings were:
Manual (using the wheel to dial in apeture as they approached)
A1 Servo (focal tracking)
Focal Length 200
Drive - High Speed Continuous
High AF point (in landscape)
ISO 100
f22
1/80
Lock you right elbow into you ribs, pan on a level plain. Keep your focal point in the same spot with motion (in this case, his helmet). I took a 5 sequence burst. I had AF tracking as he was coming around, ran my burst as he was plaining across me, and followed him even after the last frame was shot. This will take some practice, you will get it though.
Hope this helps. Sorry for the long reply. I wanted to offer some insight into the way I work and what I look for. This is not a tutorial, just what I do.
Good Luck.