What the others posted about keeping your foot off the pedal is key.
I too once wanted great gas mileage, but I decided I wanted to enjoy my truck instead of driving like a maw maw all of the time just to get 16.5mpg
Much more fun driving however I'd like and getting 14.5-15mpg
But, I have an 00 civic for sale if you really want to save on mpg! =)