For some reason or the other, my screen was failing to lock after gnome-screensaver came on. To be honest, I'd much rather just have it lock and have the display turned off instantly. This is my first tutorial, so let me know if anything is wrong with it!
First, create a scripts directory in your home folder:
Then, create and edit a new script called display.off:
Once gedit is open type the following into your script:
Save your script and close gedit, then navigate to your scripts directory and change the permissions of your script. I set mine to 750, or read/write/execute for yourself, read/execute for your group, and nothing for others (to prevent any other user from invoking the script).
#locks and puts display to sleep
xset dpms force off
Now to set the key combination, go to System->Preferences->Keyboard Shortcuts. First find your shortcut to lock the screen (should be 'Ctrl+Alt+L'), select the shortcut command and hit 'backspace' to clear it. Then click the Add button. Enter the following, replacing $USER with your username:
chmod 750 display.off
Finally, press the shortcut to change the key combination and hit the control, shift and L keys.
Name: Lock and Sleep Screen