Save gasoline - on the 1st of each month(or whatever consistently regular day you can remember), have your tires checked for proper inflation.  Discount Tire, Sam's Club, Costco, etc., offer this service on a drive-up basis.  Low air pressure can be very costly to your MPG, as well as extremely unsafe!  And have the pressure set to 5psi less than the maximum psi on the tire - not on the door panel - especially because when you replace tires, they may have different requirements than from the factory(this is very common!)

     Have your vehicle serviced with a fresh Lube, Oil and Filter(L.O.F.) every 3,000 to 5,000 miles($16, tax included, at Wal-Mart), to improve performance(hence MPG) - and make sure that the grease fittings are lubricated, as this will prolong your suspension, steering, etc.  Many shops advertise oil change specials, but do not include lubrication, because it's easier, cheaper and less time-consuming!  That's why it's so 'special!'

     Finally, I know that some Metro areas, such as Phoenix, are vast, but if it is convenient to carpool, you can certainly save money by doing so.  Some companies offer financial incentives and/or preferred parking for carpoolers.  And, as much as possible, try to plan a circuitous route for daily errands, so that you do not have to criss-cross your path, again saving time and money.  Happy motoring!