The default behavior of pretty much every camera is to activate autofocus through a half-press of the shutter button. This works perfectly well for most scenarios, but you can often improve your experience and hit rate by using a different method: back-button autofocus. This helpful video will show you why it is so useful and how to take advantage of it.
Coming to you from Jan Wegener, this great video discusses the advantages of back-button autofocus. Back-button autofocus is so named because it involved decoupling your camera’s shutter button and the autofocus function. Instead, autofocus is then activated by a button on the back of your camera (typically the AF-ON button). Usually, a photographer will use their right thumb for autofocus activation and their right index finger for releasing the shutter when using this method. Furthermore, the more advanced autofocus systems of modern cameras can often be customized even further. For example, I typically link eye autofocus to the AEL button just to the right of the AF-ON button, making it easy for me to grab a quick portrait in the midst of shooting an event or the like simply by sliding by thumb over for a moment. Check out the video above for the full rundown from Wegener.