a lot of new safeway stores sell gas and give you a 3 cent discount automatically on the price of gas at the pump if you use their shopping card which you can get for free

Flying J - these are along all major highways in the west has a discount card you can get at their website. I think it gives a few cents savings as well on gas, but for a full tank it was only about 10 cents - not much, but it helps

if you have a radio antenna, try to keep it retracted or take it off. yes, reception will stink, but in the middle of kansas I doubt there are many radio stations to listen to anyway

if you put the car in neutral or park when at stop lights, the load on the engine is reduced (no transmission engaged). your rpms should drop. i doubt this acutally adds to anything and puts a bit more strain on the transmission for changing gears, but it may help

also, don't try to draft trucks...a cracked windshield from a rock or a sudden stop by the semi can really offset the few cents you saved by reducing air resistance

also, as your crossing state lines, try to figure out the taxes on both sides of the line. For example, crossing the border from CA to AZ, it's cheaper to wait 10 miles and fill up on the AZ side then the CA side becasue the tax is lower - operating costs are about the same in both areas, but the state doesn't take as much