Before you even put the key in the ignition, plan your trip.
Many people will just hop into their car to drive to the post office, come back home and park their car. An hour or two later they get right back in and drive to the market. This scenario is repeated over and over and it shouldn't be this way. You will get better gas mileage if you combine errands into one trip since a warm engine uses less fuel. While you are at it, plan it out so you take the shortest route and/or roads with the least traffic. Google Maps and the AAA site has lots of trip planning information and maps.

Choose the right time to drive
Many times simply leaving fifteen minutes early or leaving just after the rush can save you travel time and gas. Why? because all that stop and go will use up a huge amount of gas especially if you drive a car with a V6 engine or an SUV. Check traffic reports via television, radio or through online traffic reports before leaving your home or office.

Disable All Wheel Drive
All-wheel drive or four-wheel drive is great for traction control on snowy or off-road use, but it will consume quite a bit of gas. If you are on clear paved roads then disable the all-wheel drive mode to save gas. Only use this option when weather or road conditions dictate. Avoid jack rabbit starts and stops.  This is a tough one for some folks to resist especially the younger drivers, but avoid stomping on the gas pedal when the light turns green. While it may seem cool to hear that engine rev hard, fast starts out of the line will consume huge amounts of gas as the engine has to work much harder to get the car up to speed. If you do this enough times in a row you'll actually see your gas gauge get closer to empty very, very quickly. Accelerate gradually when starting off and extend your gas mileage and the life of your drive-train.

Buy the right tires
Did you know some kinds of radial tires can help you save gas? Essentially the best tire for fuel efficiency is one that has less friction with the road. These are sometimes termed Low Rolling Resistance (LRR) tires and are made of a harder compound. The tradeoff being that they aren't as "sticky," which means the car won't hug the curve as well as you might like. Decide for yourself by reading the Tire Rack's Customer Reviews.

Keep your car's tires properly inflated
You've heard it a thousand times; for better gas mileage and to prolong their life, keep your tires properly inflated. Under-inflated tires can zap as much as one mile per gallon! The simple trick is not to inflate to what the tire's sidewall says, but to follow what the automaker says in the operator's manual or the sticker on the driver's side door.  Go out and buy a decent tire pressure gauge and check the pressure of each tire including the spare at least every month. Remember to check air pressure when the tires are still cold as the air expands when it is ht giving inaccurate readings.

Check your car's wheel alignment
If your wheels (camber) are not properly aligned you'll not only have your car pulling to one side and causing irregular tire wear, but you are also causing more drag for the engine, which results in more gas being consumed. Your car will handle more responsively after having a wheel alignment done so consider having this done if it has been a while.

Clear out the trunk of excess items
According to independent test commissioned by the US government, "An extra 100 pounds in the trunk reduces a typical car's fuel economy by 1-2 percent." It's time to clear out all those 2 liter bottles of Coke, jugs of laundry detergent from last week's Costco outing and excess tools just sitting there. It's very easy for items to keep piling up so take a moment to clear the trunk, back seat and floors. You'll be surprised at how much it all weights.

Remove third row seating
On large SUVs and mini-vans you can save gas by removing unneeded third row seating. Some of these third row seats are fairly heavy with some assemblies weighing over one hundred pounds. If you have space in the garage to store them and don't have extra passengers then take 'em out. This is extra weight your engine has to deal with, which can waste a lot of gas.