Back In The Lead
If you are leading a race and lose a spot, just "go off the track" and let the 3 seconds go by and you will be leading again.
Enter a race in Arcade mode. When you get to the finish line on the last lap, jump at the last moment. You will keep jumping until your character stops talking.
Avoid Getting Lost
If you get lost in the desert, follow Mater or any other car without bumping into them and they will take you back to Radiator Springs.