Turn off the engine if you anticipate a lengthy wait. Instead of idling at a drive-up window, park the car and go in. Idling burns more gas than restarting the engine. Limit car warmups in winter. Avoid carrying unneeded items in the trunk.
Extra weight decreases gas mileage.
Also, reduce drag by placing items inside the car or trunk rather than on roof racks. Avoid high speeds. You can improve your gas mileage about 15 percent by driving at 55 mph rather than 65 mph. Use your air conditioning only when necessary. If you have a manual transmission, the lower the shift speed, the better the fuel economy.