I had the job to shoot a mountain bike race on Saturday - the Dirty Gears Series at Harvey Bear Ranch in San Martin, California. Here is an image of one of the competitors in the Elite Division coming over a rise on a downhill section of the race.
I scouted this section of the track a 1/2 hour prior to the start of the race and set up knowing that the competitors would have a good chance of getting air over this section of the course. The challenge was, I couldn't see them before they arrived and went airborne. I would pre-focus on a spot ready for the rider to show up and then shoot fast with a shutter speed that would freeze the action of the rider in the air. I also used a monopod to stabilize the camera and allow me to pan through a series of exposures, smoothly, as the rider was passing by.