A free program called 3DEM is used to trim the DEM if needed and save it to a different format. Before you begin visit the 3DEM Website to download and install it.
Open 3DEM and go to File > Load Terrain Model
Select the file type your DEM is in.
For DEMs downloaded from USGS Seamless select GeoTiff DEM.
For DEMs downloaded from GeoComm select USGS DEM.
Go to Operation > Change Projection > Convert to UTM Projection.
Select NAD27 and click OK.
If your DEM does not have the exact coordinates of your plot you'll need to trim it. If you used the USGS Seamless Site and entered the exact coordinates skip to saving the DEM.
Go to Operation > F8 Select Smaller Region.
Move your mouse cursor until it is precisely at the NW coordinates that you wrote down earlier.
Click and hold down your left mouse button.
Drag downward to the right until you get to the SE coordinates.
Release the left mouse button and hit Enter on your keyboard. The full DEM is replaced by the smaller area you selected.
