One of the most effective ways to increase how far you can stretch a gallon of fuel is to improve the way you drive your car. Simple things like switching off the air conditioning and heated screens when they're not needed can make a significant difference to your fuel economy, but so can you. Take a look at how you drive and try and learn to be more efficient behind the wheel. Plan ahead, slow down and use the natural terrain to your advantage.
Planning ahead allows you to keep moving while others stop and go. Keep an eye on traffic light sequences or even leave a little bit earlier to get to work to avoid traffic snarl-ups. Idling in traffic is the enemy of efficient driving. Slow down too; a few mph off your top speed can make a big difference to your mpg. Use the terrain effectively - momentum is your efficiency friend, though don't be tempted to knock your car out of gear to coast as it removes control and uses no less fuel than being in gear and being off the throttle. Drive wisely and the fuel bills should plummet.