Just because you have an auto focus camera, even if it has a 45 auto focus point system, that does not mean that the camera always knows where to focus.
Use the AF focus points in your camera carefully and make sure that the most important part of the scene is in focus.
When it comes to a person (or an animal) the main focus point is usually the eyes.
Don’t overlook the importance of the Focus Lock feature on your camera, which lets you lock in the focus on a particular part of the scene, after which you can recompose the scene and take the picture. Setting individual focus points can be advantageous, too.
Careful focus is especially important when photographing people (and animals) with telephoto lenses set at wide apertures and when there are foreground elements in the scene - as illustrated by this photograph I took of a Huli Wigman in Papua New Guinea.
Explore the light,
P.S. The catch light in the man's eyes were created by our guide holding a reflector. When possible and appropriate, I try to add catch light to a subject's eyes. You can also add catch light with a flash, or by having the subject look toward the direction of light.