I switched to using back button focusing about a year ago and now I never want to go back. [Sean]
From the Canon Austalia YouTube Channel:
Learn how to back button focus with this step-by-step video guide by Canon Collective Ambassador, Kass Brumley. With this video guide, you will learn how back-button focus works, use cases and how to set it up on a Canon EOS 5D Mark IV and similar models.
These are the key steps to follow in order to set back-button focus:
Step 1: Disable Autofocussing from the Shutter Button - 1:53
Step 2: Select ‘Metering Start’ - 2:13
Step 3: Assign Your AF-ON Button - 2:33
Step 4: Select a Focussing Mode - 2:53