The pilot of a Piper PA-28-140 stated he estimated he had about 12 gallons of fuel when he started the airplane and departed to attend a breakfast fly-in. He climbed to a cruising altitude of 2,500 feet for the planned 35 to 40-minute-flight.. When he was between 3.5 to 4 miles from his destination airport, he initiated a descent down to 2,000 feet and leveled the airplane. The engine sputtered and he initially thought he had a problem with carburetor ice. He applied carburetor heat, turned the boost pump on, checked the mixture was full rich, pumped the throttle, and the engine stopped. He initiated a forced landing to the trees when he realized he could not land at the destination airport. The pilot stated he did not have any mechanical problems with the airplane before the accident and "the loss of engine power was due to fuel starvation." Examination of the airplane by a Federal Aviation Administration inspector revealed that the left and right main fuel tanks were not ruptured. No fuel was present in the left main fuel tank and about 1 cup of fuel was present in the right main fuel tank.