GasBuddy.com is your Friend.

With gas prices stretching ominously towards the $4 mark, driving can be one of the the more difficult areas to cut costs, especially in California. I've got a 40 minute round trip commute to work and a 1hr 20min round trip commute to my boyfriend- so even on my most conservative gasoline behavior I've got to fill my tank at least once a week. The gas stations closest to my house and work tend to be more pricey than those further afield, but by scheduling my fill up to happen on the way to Boyfriend's house or on a day when my errands take me outside of my usual routes, I can save anywhere from 30 to 50 cents on gas.

My secret? Gas Buddy, a site where members update fuel prices. When gasoline first shot above the $3 mark, I was still paying $2.70 or $2.80 and filling up for less than $30.

Another good habit is filling your tank at the quarter tank mark. For one thing, it's gentler on your car (driving around on fumes during that last hour before hitting the pump makes your engine sad), and secondly it's a built-in savings of almost $10. If you ever have a week where every penny counts- think of it as gasoline insurance- you can use up the quarter tank when you just can't afford to fill up until your paycheck clears the bank.