Get to full speed (preferably but not necessary) and press 'N' for
 neutral. Now you can cruise along at full speed with easy steering
 and invulnerability. As long as you stay in neutral you will have
 unlimited time as well. 
 
 Another trick is to repeatedly hit the 4 key (4th gear) until the
 program has an error. Continue with the right mouse button. Repeat
 until you get a high score.