Familiarity with the aircraft led to a level of complacency on my part…[with] the fuel selector switch and checklist flow during preflight. My belief that the selector switch was always on BOTH allowed the checklist item to go unnoticed. The…flight [was] conducted with the aid of the autopilot, which prevented me from noticing the aircraft flying more and more out of trim while one [fuel] tank was being exhausted. Approaching the airport and disconnecting the autopilot, [I] noticed the trim situation, which was promptly overshadowed as the engine lost power. Ground proximity, aircraft configuration, airspeed, and the urgency of the situation prevented me from attempting corrective measures that might have restored engine power.