Learn how lat/lon & UTM coordinates work, carry a good gridded map, and then all you'll really need is point position from your phone's GPS.
That's a really good point. I now have an iPhone app (
Tom's GPS) that will display your location using UTM coordinates. Other than saving waypoints (like the location of the car, camp, etc), I primarily use my GPS to give me the UTM coordinates so I can pin-point where I am on my map.