Gas mileage in new Jeep and old Chevy

Any suggestions to increase the gas mileage in a 2001 Jeep Wrangler Sahara with a 4.0 liter 6 cylinder motor? I only get 18 mpg in town, and 22 on the highway.

Along these same lines, any suggestions for increasing the gas mileage on a 1968 Chevy C10 pickup, 2WD with a 250 cc, inline 6 cylinder in it? It's got a single barrel Monojet carb, straight pipe exhaust.

Love to hear what anyone out there has to say.