Is there a quick way to lock my Mac?

Solution 1:

On macOS High Sierra, there is a standard key sequence and Apple menu item to lock your screen.

• Control-Command-Q or ^+⌘+Q

For older OS, ⇧+⌃+⏏ puts the display (only the display, not the whole computer) to sleep and will then prompt you for a password if you have enabled Require password [amount of time] after sleep or screen saver begins under System Preferences > Security.

If your Mac does not have an ⏏ (eject) key, you can use ⇧+⌃+⌽ (power).

Solution 2:

From my answer in Super User.

Using Keychain Access's Lock Screen menubar.

Activate it here, in Keychain Access.app's Preferences:

Then lock.