Looking for a better way to focus your DSLR? Try using back button autofocus. It’s a faster, easier way to get great AF results from your DSLR.
Decoupling autofocus from your shutter release can take your photography to a whole new level. The best part is that this method will work for a camera a dedicated AF-ON button or by reassigning a button on the back of your camera.
Most people focus their DSLR camera by pressing the shutter release part-way down, holding, recomposing and pressing down the rest of the way to release the shutter. I’ve got another way to autofocus and I think you might just like it a little bit better.
We’ll start by disabling the autofocus function for your shutter release and switch it exclusively to a button on the back of the camera. This completely separates your autofocus function from your shutter release. It’s called back button autofocus.
In my opinion, this gives you much more immediate control over autofocus. I can’t even imagine going back to shutter release autofocus. This way is so much better.
I am much better at showing than telling, so I’m going to give you a link to the video I put together that explains why it works and how to do it.
Click here for my complete video tutorial. 
You can also head on over to my photography site, Backcountrygallery.com  and check out some questions and answers about this technique. Look around while you’re there, I think you’ll enjoy what you see.