[mozillas]

Control+Shift+Power turns off the display and by checking "Require password after sleep or screen saver begins" in System Preferences you get same effect by using a keyboard shortcut. https://apple.stackexchange.com/a/46170

[eugeniub]

Personally I prefer hot corners because I can lock it with one hand, sometimes as I'm in the middle of getting up.

[jiaweihli]

Ctrl-cmd-q locks out of the box, no customization needed.

[_asummers]

I do a shift modifier on mine and then just throw my pointer into the corner. Works well enough for me!