It seems that one of the often forgotten to-do's is to capture a waypoint for the parked car or the trail head before you head out ... so you can get yourself unlost. It also give you a chance to check the GPS battery level before heading out.

I recently has my Garmin NUVI GPS direct me down a rarely used gravel road and then across a grassy field while driving through a crazy hilly and rocky state park in southern Illinois. Venturing down the gravel road was fun (4WD truck), but I turned around at the grassy field. Common sense prevailed!