Unfortunately some of us have to drive large trucks either because of climate, work, location, or any combination of other things. Most of these large vehicles get very poor mileage, but but with proper care and maintenance we can improve it slightly.
Step 1: Get a topper or cover for your truck
Mythbusters have proved that these aren't the most fuel efficient when the truck is empty, but they didn't try it when it was full of wood or old appliances. A topper can really help when you are hauling bulky unaerodynamic objects by reducing the drag from wind.