Okay, so... I've known about back button autofocusing for a while now, but never quite grasped it. I kept seeing articles and posts online about it and figured there has to be something good going on here. I stayed curious and decided to give understanding it another shot.... This morning I Googled, and now I sigh in relief. I get it!
On recent shoots involving children I found myself wanting to switch back and forth between single focus, where I can set my focal point, press the shutter button half way and recompose if I like, and continuous mode which works better when the kiddos are on the move. Going back and forth having to decide which mode to use was annoying and I was possibly missing opportunities.
Simply put, switch your camera to continuous mode, go into your menu to autofocus-AF activation and choose AF-On only. Now instead of pressing that shutter halfway use your thumb to focus by pressing the AF-ON button (back of camera, right where your thumb would like to be ; ) ). Press once to focus then you can recompose several times if you like and keep shooting without having to find focus every time. Say your subject is on the move just hold down the AF-On button as you follow and click away. I'm sure it's going to take a little getting used to, but definitely worth it!