I am a control freak. When I shoot, I like to have as much control over my photo as possible. I use primarily aperture priority mode to control my depth of field though will switch over to shutter speed priority when I am shooting an image where I need to stop action or where there may be movement in the frame that I do not want to capture. I also often use full manual mode which allows me to control both aspects of my exposure independently of each other. I shoot RAW to ensure I have complete control over how the image is processed. For my macro photography, I manually focus to ensure that my focus is always exactly where I want it. For much of my other photography though I use auto focus, but I still control that aspect of my photo.
The default mode for cameras that offer selective focus points is usually either the center focus point or all focus points. The problem with using the center focus point is that is not conducive to good composition. Sure you can focus on your subject using the center focus point then recompose your image, and if that is the only option you have, it works, but I think that people in general will not do this on a regular basis. Using all of the focus points your camera offers can cause problems for you as well. While you know what part of the subject you want to be in sharp focus, the camera does not and so may focus on a different part of the your scene than you would.
By turning off both of these options and selecting one single focus point, I can be sure that where I put my focus point in my photo will be sharp. My camera offers 5 focus points across the middle of my frame and one centered above and below the middle. I generally the focus point second from the right though of course, it is really determined by my image. For portraits where I want the eyes sharp, that will be the focus point used most often as I tend to shoot most of my portraits vertical and that particular focus point lines up almost right in line with where I want the eyes to be place in my image.
Camera manufacturers all have different methods of selecting focus points. To find yours, refer to your manual.
Until next time, happy shooting.