First, look for local deals. Search for things like rewards programs for place you go all the time that partner with a gas station. Lots of grocery stores will give you points that you can cash in at a certain point for a discount on gas.
Second, use gas station credit cards. Most gas station credit cards give you 10% off at the pump as well as rewards points when you use the card. Just make sure you pay it off within the grace period so you don't get charged interest while you're trying to save money.
Finally, use your smartphone! There are a slew of apps that can help you in the car. There are apps like GasBuddy which will show you the 10 cheapest gas stations near your current location.
Don't forget Carticipate. It's a carpooling app. It helps you find people like you who can carpool together. As gas prices head up into the summer months, these tips can really pay off.