Consider weight loss and amputate that lead foot.

Try these as well:

Remove the rear and passenger seat.

Toss out the spare.

Eat one less sandwich at lunchtime

Drive under 55mph.

Keep your tires to 32psi cold. all around.

Go with lighter 17 or 18"s wheels.

Drive with the windows closed.

remove the sub in the trunk.

Drive naked (not recommended in some states, especially if youre ugly).

Get a wheel alignment.

Never offer to drive anyone.

Use premium fuel.

Drive with both hands on the wheel (rather than ghetto style one hand on top)

Sit upright instead of in a lawn chair position

Keep your radio and other unnecessary electronics off while driving.

Thats all i can think of for now... enjoy.