I love the way this works, the grass either side and the path all lead the eye to the boy. Really well spotted and composed. As said above this may look better if the subject was on a third and so I have uploaded a mod to demonstrate this. I also made the sky more blue and applied unsharp mask to help sharpen up the boy.
As Focus_Man has suggested set your camera to spot focus then place the boy's head in the middle of the AF frame in your viewfinder and press the shutter button halfway. This locks the focus and allows you to move the camera to compose the image how you want it. Press the button fully and your subject will be in focus no matter where it is in the frame.