I bet you have been told to buy gas very early in the morning or late at night will get you more fuel because of capitalizing on the density of gasoline at lower temperatures. From what I can find out that doesn't really make a difference. They do tell us that gas is denser at lower temperatures however, most stations put their tanks several feet underground, so the temperature isn't likely to changes very much.
I have noticed that the price of gas seems to go up around the weekend and or holidays. I keep track of this and fill my tank in the middle of the week. Keep a close watch at your local gas station and see when the prices change, then you will know when to fill up your tank.
Many times using local transportation can be even cheaper than if you drove your own automobile. Some cities offer transportation discounts for certain users. Carpooling is also a great way to save on the cost of fuel. There are ways to beat the rising cost of gas prices, just check around your local city and see what is best for you.