Welcome to ecomodder .
As always, the best start is to read the list of hypermiling tricks :
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
and read up a bit about them in the appropriate forum.
Take a few of the tricks you feel comfortable with, and try them out on the street. When they've become a new habit, revisit the list and pick up a few more tricks.
This is very much a hands-on forum
You've already done trick
6) Join a fuel economy forum
Another tip is to start a fuel / modifications log and maintain it rigorously.
If you have a manual transmission car, coasting (even with the engine on) is something you should really try out.
Then there's the list of possible modifications to be done to the car
65+ Vehicle modifications for better fuel economy - EcoModder.com
The most common mods are increasing the tyre pressure, and fitting a grille block (can be done from the inside if you want to keep a clean look) and air dam.
The mods done range from mild, to wild - just search for AeroCivic
You can go as far as you're willing to go, but it's always tempting to go a bit further.