try taking your foot off the gas and slowing down before coming to a red light, stop sign cross work etc.
Speed
Don't drive over 60mph/95kmph
Extra Weight
Remove any extra weight that is in your car.
Clean out your trunk.
Clean out the back seat.
Your car should not be used as a storage room..
Idle
Don't over idle your car.
Cruise Control
Use the cruise control
Overdrive
The over drive gear it will decrease your car's engine speed and therefore save you money.
Car maintenance
Air Filters
Change your cars air filter ever 12000Miles/20000kilometers.
If you drive mostly on dirt roads or where there is a lot of dust, then change your cars air filter every 3000miles/5000kilometers.
Tires
Keep the tire pressure at the right pressure.
Check your car's lowers manual or ask your service station what is the correct air pressure for your tires. Each car and tires are different.
Motor Oil
Use the correct type of motor oil for you car.
Fuel Cap
Make sure the fuel cap on your car is sealed the way it should be. If the fuel cap is not sealed properly, then you could have gas evaporate from your tank.
Use the correct octane level for your car. it is not necessary to use a higher lever octane, then needed.
Organize
Try to organize all your trips, so you can make as few trips as possible.
The car uses more gas to warm up the engine, then it does to drive with an engine already heated up.
Air Conditioner
55mph/95kmph or less
Don't use the air conditioner - try to open the window