Although I've been a Mac user for a couple of years, I recently switched over fulltime to a Mac as my primary development machine at work. There are a lot of things I can get away with on a personal machine that I can't on a work machine (e.g., walking away from my laptop with the screen unlocked).
I was shocked how long it took for me to piece all of the little bits from various Google searches to create a simple keyboard shortcut that allows users to quickly lock their screen, so I thought I would compile it in one [hopefully] simple post.
The following shell command will return the current user to the login screen.
/System/Library/CoreServices/Menu\ Extras/User.menu/Contents/Resources/CGSession -suspend
There may be easier/better ways, but I decided to place this command in an Automator script, so launch Finder and open the Automator application.
Choose the Service type at the launch screen:
Toward the top-center of the window, look for the drown down box next to Service receives and select no input from the drop down list.
Under Actions -> Utilities, drag the Run Shell Script task to the right pane.
Paste the following command into task window: /System/Library/CoreServices/Menu\ Extras/User.menu/Contents/Resources/CGSession -suspend
Save the script as Lock Screen and quit Automator.
Back in Finder, go to Applications -> System Preferences -> Keyboard and select the Keyboard Shortcuts tab after the application launches.
On the left-hand side, select Services
Scroll to the General category from the right pane and select the Lock Screen service to select a keyboard shortcut.
Simply click the add shortcut button to assign a shortcut. I went with Command + Shift + L, but do whatever makes most sense to you.
And that's it! Hope this helps somebody.