Read your owner's manual and use the level of octane recommended. Know what level of octane constitutes "regular" or "premium" in your state. Slow down and accelerate and brake gradually. Keep your car well tuned, your tires properly inflated and your trunk empty. Try a gas station credit card that offers a discount and ask about gas vouchers. Note whether gas prices in your area fluctuate depending on the day of the week. Be skeptical of "gas-saving" products. Go to www.ftc.gov for more information.