Pick a Special Part that you can hit yourself with like the Missile or Landmine. When you enter the race as the camera is zooming in on you use your Special. After it hits you'll be in "ghost" mode and you can start the race a few seconds before anyone else.
Once you get to Class A you can get a Special part that looks like a Silver Diamond. (Should be a Picture in Images) It targets the racer in First and spins him out. Once you get it to level 3 and get in First it can still be used on the racers behind you(without using any "ammo") causing them to crash. It can be used over and over which allows you win very easily. The Crown also helps as it starts your Special at level 2.