yeah, it all depends on the car too...
some engines perform better in real low RPMS and others work better in the mid range...
some ECUs have a good low throttle fuel map, while others are more efficient with more air
some trannys are geared for acceleration with little power, while others are geared for cruising with low rpms..

all of those differences along with other different details make it impossible to come up with a "this is how you get the most mileage out of any car" type of thing... i mean other than the general don't lead foot it off of the line and don't accelerate to a stop and pay attention to bumps so you don't want to bounce your foot on the pedal...