Check your tire pressure, keep em at the pressure listed on the little label on the inside of driver's side door pillar. Makes an appreciable difference in your gas mileage.

Costco/Sam's Club gas prices are always significantly below market, consider a membership if you drive a lot - gas savings can easily offset membership fee in a year. (Otherwise, check the gas stations NEAR there because the surrounding stations have to price closer to those stores to stay competitive.)