Here are some ideas…
a. Keep the air filter clean.
b. Keep the car in tune… change spark plugs… new cap and rotor… new wires.
c. Drive softly… easy take offs… gradually building speed and keep speed low… use brakes very little (brakes convert gasoline energy to heat and exaust that enegy to the enviroment–wasteful).
d. Avoid 10% Ethanol fuel mixes… Alcohol burns with less oxygen… it burns much richer… 14.7:1 (fuel to air weight) for gasoline… about 19:1 for alcohol… so you lose fuel economy (about 5% less than pure gasoline). Also unless you car is specifically designed for alchohol use (Flex fuel) you car will suffer some corrosion to fuel filters, aluminum fuel lines, injectors, etc that will become apparent someday.
e. You improved the efficiency of you air intake… you can improve the efficiency of your exhaust too… tuned headers and a low flow resistance exhaust system will improve your fuel economy further.
f. The Fitch Device… the only device has a number of benefits including the ability to burn a lower octane (cheaper fuel) without pre-ignition problems. Look into that… do a search on Google for “Fitch Device”. I think the only device on the market that has some measureable benefit.
g. Keep track of your fuel economy in a log or spreadsheet.