Mac: If you're finished working with your Mac for the day and want a quick way to turn off the monitors or put your system to sleep, you don't need to use a hot corner or special app to do it, just a keyboard shortcut.Photo by Declan Jewell.
Press Ctrl+Shift+Eject to put your Mac's displays to sleep immediately, with no warnings or delay. If you're really finished working and want to put your entire Mac to sleep, press Opt+Cmd+Eject to instantly put your Mac to sleep.
While the Mac has no consistently effective keyboard command to lock the screen, you can set it to require a password to wake up from sleep (System Preferences > Security) and combine it with the instant-sleep shortcut to get the same effect.
Shortcut of the Day highlights a great shortcut on various platforms from the desktop to mobile devices to the web. You can find more shortcuts here.