GPS, UTM and USGS topo maps

Draw in the UTM grid lines on your USGS topo map.
Each box is 1 km x 1 km.
Set up your GPS to use NAD27 datum and UTM coordinates.
With CalTopo maps you can add and print NAD27 UTM grid on topo map. More info on using UTM, or here, and guide and tool or print this on a transparency or pdf.

Though you may not have cell-coverage in the backcountry, there are mobile apps where you can preload topo maps and still use the GPS on the cell phone. On my iPhone I use iHikeGPS

Tennessee landforms
Bring a compass. It's awkward when you have to eat your friends.