If you have a second display you may have noticed that from time-to-time it seemingly ‘takes over’, i.e. your dock, quick app-switcher, spotlight search and so on move over to the other screen. This is annoying!
You can stop this happening by going into System Preferences > Mission Control and deselecting Displays have separate spaces. You can find more info about Spaces here.
However, I don’t like the way this works - I actually prefer my displays to have separate spaces. This means I can quickly switch between Spaces on my main display, but my second monitor stays as it is with open apps that I always want to be able to see (such as my terminal, or Flowdock or whatever).
So what now? Well all is not lost - there’s a little known method that will quickly bring ‘control’ back to your main display.
Simply make sure you are ‘on’ your main display (click on the desktop for example), then move the mouse cursor from the top, to the bottom of the screen. In doing so you should find that the dock switches back to this display (and the app-switcher, spotlight search etc.).