hrmm...one thing is keep the speed down, especially on the highway/freeway. a coasting speed of 80mph is probably somewhere around 20% less fuel efficient than a coasting speed of 60. it may be tempting to blaze to work on an open road, but the combination of fuel inefficiency and the possibility of getting yanked by the coppers usually negate any time savings.
make sure to keep the tires properly inflated and, if you've got a spare set, maybe it might be time to put the steelies back on (well, i suppose this is debatable, as the increased diameter could be more efficient at fwy cruising speeds? either way, a tire with a narrower contact patch will give less resistance and be more fuel efficient).
stuff like mentioned above about maintaining the car properly
take off that nasty spoiler that you've got on the hatch (i, however, do not follow my own advice and have kept my wing on -_-
when going at freeway speeds, windows up to increase aerodynamics. at cruising speeds, using the a/c (if you've got it) is slightly more efficient than driving with the windows down. in city driving, however, a/c is a fuel economy murderer.
drive smoothly--no abrubt downshifts. accelerate smoothly and try to keep the revs low.
shift into high gear as soon as possible? if it doesn't make the engine bog, then being in high gear is great. if the motor is struggling, you're probably doing more harm than good. when my cousin had the VAFC or whatever those apex units for vtecs were, we looked at the little graphs and found that being in 3rd gear at Xmph used less fuel than being in 4th gear at Xmph where X was kinda slowish. yeah not very exact, i know, but the concept makes sense...if the motor is struggling, it's not operating at peak efficiency, which is more than likely a bad thing for fuel economy.
remember, either way, we're in better shape than those peeps driving their, how does kwicko put it? oh, that's right. we're in better shape with our rexes than people who are stuck driving their sport futility vehicles. i love it when gas prices go up (i'm a huge proponent for "we-don't-take-over-other-countries-for-lower-fuel-costs" pricing as they've got in europe) and i see the guy in the h2 spending triple digits on gas. it makes a little tear of joy well up in my eyes.