First,
read the sticky at the top of the forum...
Look at the sticky in the aerodynamics section also. Those two will answer most of your questions.
The biggest way is to not drive. The second biggest way is altering driving style (driving w/out brakes, optimal acceleration, 55mph max speed, etc.). The next alternatives are vehicle modifications. These can range from pumping up tires to max+ sidewall pressure to building a boattail.
If you are mechanically inclined, you might think about dropping in a d15z1 w/ an HF transmission. Adding lightweight vx tires will also help.
- LostCause