Drive conservatively. Don't gun it unless you really feel the need, accelerating moderately will help your mileage. Also, throw it in neutral downhill, when you see a red light up ahead, etc. I'm not actually sure if that actually helps, might just run your brake pads out faster. But I know when my wife drives my car she gets about 27-28MPG, I get about 33-34. I drive fast, but I don't push the engine like the little lady.