Gas prices keep climbing. They are $3.69 here for ethanol. Since we live in the country we have to drive at least ten miles to get anywhere. The last time gas prices were this high, a couple of years ago, one of the morning news shows had two cars leave Chicago and drive to New York. One drove normally--speeding slightly, starting and stopping normally, etc.-- the other drove with science in mind and saved gas, got there just a couple of hours later. I don't remember all the details, but a few facts stuck with me and I try to abide by them, especially in times when gas prices are up.
Whenever you will be sitting idle for more than 30 seconds (like in a drive thru), shut off your engine. Thirty seconds is the magic number. If you will not be idle that long it actually takes more gas to restart the engine than to sit idling for less than 30 seconds.
Fifty-five is the speed that your car runs most efficiently. This has to do with drag and aerodynamics. The details bore me, but if you go slower or faster you will be less efficient.
Starting and stopping should be done gradually whenever possible. I try to watch my rpm and keep it in check. This also has to do with physics and inertia. (One of Newton's Laws of gravity, maybe. High school science was so many years ago...)
Coasting down hills and refraining from running heat or AC if possible, both also help your gas mileage.
I know there is debate about whether it is better to run AC (uses more gas) or to drive with windows down (creates drag, thus uses more gas). If I remember right it depends on your speed and duration of the trip.
One thing that I heard and haven't really been able to prove is that Wednesdays are the best day to buy gas as it tends to go up as the weekend nears.
Keeping your tires at the right air pressure will help your gas mileage. Check them regularly. Also take care of the fluids so that your engine is running at its best.
Plan your trips to be most efficient. If you are going to be near the grocery store, get groceries then instead of making a separate trip later.
I believe any little thing can help. I certainly don't do all these things all the time, but I do try to be mindful of them. I hope you see something that will help you. Please share other tips you have relating to gas prices, gas mileage, or similar topics.