We don't recommend that GPS units be taken on a PCT thru-hike. It's hard to justify the weight on such a well-marked trail. Besides, GPS units have batteries that die, software that crashes, watertight designs that fail, and a propensity to sink if they fall in lakes.
If you are determined to use a GPS, be proficient with your particular unit before starting your trek. Also, before your trip starts, reference Halfmile's maps, Google Earth, and National Forest Service GPS data to find the GPS coordinates of every significant landmark, campsite, resupply point, fresh water source, et cetera along your route and load these into your GPS unit as waypoints.
GPS coordinates come in three formats:
For example, these coordinates are written differently, but refer to the same campsite at the north end of Anclote Key on Florida's Gulf Coast:
The formatting of coordinates in Google Earth can be changed by going to Tools and then Options. To change the formatting in your handheld GPS unit, refer to its user's manual. If for some reason you need to translate coordinates from one format to another manually, click on the calculator icon to use the Latitude & Longitude Coordinate Converter
Never ask another person for directions unless it is another thru-hiker. Not out of stubbornness or irrational male pride, but something you'll learn from experience. Non-hikers get around in cars and simply have no idea how far something is on foot.
Invariably, people give estimates in time, not distance. "It's only five minutes up the road," they'll say. Well, they mean five minutes by car, not on foot. 55mph equals 80 feet per second. I don't walk that fast, and I doubt you do either. So five minutes by car is 24,000 feet, or 4.5 miles—that's over an hour of walking.
To circumvent this inevitable problem, make sure to have maps of all trail towns, with distances marked to key locations like supermarkets, motels, and laundromats.