USGS Maps and GPS's
The USGS Map Stores sell 1:24,000 maps for $8 each. They are 7.5 minute maps.
You can use your GPS Long/Lat set up but its much easier to use the UTM (Universal Transverse Mercator) Grid set up on your GPS instead of Long/lat.
Loot at the top of the maps, you'll see the Easting and Northing 1000 meter grids every 1000 meters.
It will looks something like this: 346000E on the top and 4164000N on the side.
When set on UTM your GPS will give the same readings.
Now you have (or should have) your compus with you also. Get one with the 1:24000 scale.
Or get a map scale/templet with a 1:24000 Scale.
The UTM will show on the map as 1000 sq meters. You're compass will brake it down into 100 or 10 meters (depends on the compass).
I've found this more accurate and faster then trying to line up your Long/Lat on the map, even if you draw Long/Lat lines across the map.
Just a tad bit of information I pass out in my map reading/Land Nav classes.