There are four Race Tournaments in GTA San Andreas. When you enter the map marker for the tournament, select a race from the menu, which provides info about the length of the track, best time and position (if you've attempted it), and a small map of the course. There is no limit to the number of times you can attempt a race.
If you vehicle is destroyed, or you destory an opponent's vehicle, the race is failed. If you exit your vehicle, you will have 25 seconds to re-enter it, or the race will be failed.
Each race is a different course. You must pass through a succession of markers, and you must pass through a marker to activate the next marker. Each race carries a reward of $10,000.