How to lock Mac OS X quickly using a keyboard shortcut
Although not widely known, it is actually possible to lock Mac OS X quickly and easily by pressing the keyboard shortcut: 'Control + Shift + Eject'.
This keyboard shortcut actually puts the display to sleep, however if the setting 'Require password after sleep or screen saver begins' is enabled and set to 'immediately' in the 'Security' system preference pane, then Mac OS X will lock the session and prompt for the password to unlock the screen when you resume the session (i.e. moving the mouse or pressing a key on the keyboard to wake the display).
Note that when enabling this setting, if a screensaver is set, Mac OS X will automatically lock the session when the screensaver appears (at the time delay set in the 'Security' preference pane). To prevent this from happening, and for Mac OS X to lock the session only when you press the keyboard shortcut to put the display to sleep, you'll need to disable the screensaver.
For step-by-step instructions with screenshots, check out the following article: OS X Daily - Lock a Mac Screen
Although not widely known, it is actually possible to lock Mac OS X quickly and easily by pressing the keyboard shortcut: 'Control + Shift + Eject'.
This keyboard shortcut actually puts the display to sleep, however if the setting 'Require password after sleep or screen saver begins' is enabled and set to 'immediately' in the 'Security' system preference pane, then Mac OS X will lock the session and prompt for the password to unlock the screen when you resume the session (i.e. moving the mouse or pressing a key on the keyboard to wake the display).
Note that when enabling this setting, if a screensaver is set, Mac OS X will automatically lock the session when the screensaver appears (at the time delay set in the 'Security' preference pane). To prevent this from happening, and for Mac OS X to lock the session only when you press the keyboard shortcut to put the display to sleep, you'll need to disable the screensaver.
For step-by-step instructions with screenshots, check out the following article: OS X Daily - Lock a Mac Screen