I simply select a few games I don't play very often, and click the "Right Arrow" button.This fires off a few command line windows - please let them run to completion.Select “Backup and Restore…” and pick “Backup currently installed programs” from the next dialog.You’ll be presented with a window that lists all of your installed Steam software. Right clicking installed games directly from the library listing also works; just select “Backup Game File…” as a shortcut.That’s a bad thing to do, but it’s also understandable.Every company has moved to exclude class action lawsuits ever since the United States Supreme Court struck down a California law that forbids companies from excluding class action suits in their terms of service.Use shift or control for multiple selection with this method. In addition to picking a device with sufficient remaining space, keep in mind some older file systems such as Fat32 have inherent file size limitations (4GB, in Fat32's case).Consider converting these devices to newer file systems such as NTFS when possible.
Note that Steam Mover can be used to move any folder around (by changing the Source Path), but for Steam the maximum benefit is in moving individual games from the Common folder.
Once finished you’ll be presented with the option of opening the backup folder and given basic instructions on restoration. Select “Restore a previous program…” from the Steam menu “Backup and Restore Games…” option, and select the folder where the backup was stored.
You will see all backups kept in this location reflected in the next window as confirmation.
Or do you have a super-fast SSD that is too small to hold all your steam games at the same time? Following on from a very interesting post on the Steam forums I've created a little app to make moving the files and creating the junction points much much easier!
Here I have my steam folder in the default location, and the application should find that for you.