First, know when to fill up. According to Marshall Brain, founder of HowStuffWorks, a consumer guide, you need to time your fill-up. Most gas stations change their prices in the morning, usually between 10 a.m. and noon. So if gas prices are moving up, the best time to fill up is in the morning -- before the station increases its price.

If, on the other hand, prices are falling, wait until the afternoon or evening. With the current drop in prices, I saw a station drop its price by 18 cents in one day. If you had filled up that morning, you would have spent an additional $3.60 on a 20-gallon tank versus filling up later that evening. (Tip: Many new cars will operate more efficiently for a lot longer if you fill up when the gas tank is a quarter full. Going lower will pull junk up from the bottom of the tank and gunk up the gas lines and fuel injectors over time.)

Second, when prices are rising, fill up more often. If you typically fill up when the tank is one-quarter full, fill up when it's half full instead. This won't save you a lot of money on each fill up, but it can save a lot over time. When prices are falling, do just the opposite. Wait as long as you can between fill-ups. This will give more time for gas prices to fall. When prices are dropping fast, this can save a lot of money.

Third, don't fill up on weekends. According to Marshall, gas stations, especially those close to the highway, will often elevate their prices on weekends to take advantage of travelers.

And finally, be aware of gas station tricks. According to the Boston Globe, some stations are changing the names of their gas. Instead of "regular," they use "economy," and then call their mid-grade gas "regular." Unsuspecting customers reach for the "regular" and end up spending 10 to 20 cents more per gallon. The key here is to pay attention to the octane number. Most cars, even the high-performance Porsches, operate just fine on the lowest octane gas. In some cases, the "economy" and the "regular" will have the same octane level. Obviously, buy the cheaper gas.