One thing I’d like you to know about me is that I’m lazy.
In fact, lazy enough that the extra step of extending my hand from the keyboard to my monitor to turn it off before I go out for a bit (and doing the reverse when I come back) is already bothersome for me.
So, in typical Linux fashion, I looked for a way to force my monitor to sleep.. and map it on my keyboard.
In System > Preferences > Keyboard Shortcuts, I have:
Name: Monitor Sleep
Command: xset +dpms dpms force off
and I mapped it to, aptly, Pause / Break.. which is what I do when I press the button.
Try the command via CLI first before mapping it since I’m not sure if it came with the default X11 installation. If not, you can install it via:
# apt-get install x11-server-utils
Laziness is a virtue, methinks.. sometimes. D: