By default with most DSLRs, your shutter button is what you use to focus, take a meter reading and take your photograph. This is a lot of tasks accomplished by one button, and it can lead to some problems when shooting portraits and events.

After shooting for years, I discovered something called back button focus and it has been one of the most profound and beneficial changes to my shooting style. This allows me to move focus to a different button on the back of my camera to be quicker and more accurate with my focus controls!