Check out the videos by Terry White showing 10 things that beginners want to know how to do in Photoshop & Lightroom:
From Jim Harmer's 'Improve Photography' website. Jim says "One of the most frequent questions I have received in the last month has been about back button focus and how to use it on Canon and Nikon DSLR cameras.
In this article you’ll learn what back button focusing is, and how to back button focus for Canon and Nikon cameras."
Tip - George Evancho