Take roof racks or luggage boxes off your car when you aren't using them.
If you are going to be stationary for more than 30 seconds, switch off your engine.
Keeping your tyres at the right pressure saves fuel, as does regularly getting your wheel alignment corrected. Keeping your engine well tuned helps improve your fuel economy.
It sounds obvious, but a heavier vehicle means more drag. Leave heavy items from the boot at home when you're not using them.
Look ahead, maintaining a safe following distance and you'll keep at a more constant speed. This used less fuel than constantly accelerating and breaking.
Reducing your speed by 10km/hr can knock around 10% off your fuel consumption.
Accelerate smoothly. Change gear early, but don't labour the engine. If you drive an automatic, switch overdrive on as this will keep the engine speed down.