Here are you talking about the gas that we use in the cars? Or is it gas that we use in the house. Let me answer both because i don't know which one you are asking about.
For the car, the one think i learned, is that when you are purchasing a car it's good to check the fuel consumption before you purchase it, that is the first and most effective way of saving on gas. Avoid getting into jams, that is one way we consume fuel when the engine is running and your not moving, you will consume a lot of fuel. If you have to go somewhere with your car wait until rush hour is over then start moving.
For gas at home always make sure the pipe that is used with the gas cylinder is well secured and there are no openings that can cause gas leaks. Also check the nobs and make sure they are switched off properly not halfaway. This way you can be able to know the consumption you use for a period of time.