The single most important - and frequently overlooked - full swing fundamental in golf is the setup position.
At address your body (feet, knees, hips, forearms, shoulders and eyes) should be positioned parallel to the target line. When viewed from behind, a right-handed golfer will appear aimed slightly left of the target. This optical illusion is created because the ball is on the target line and the body is not.
The easiest way to conceptualize this is the image of a railroad track. The body is on the inside rail and the ball is on the outside rail. For right-handers, at 100 yards your body will appear aligned approximately 3 to 5 yards left, at 150 yards approximately 8 to 10 yards left and at 200 yards 12 to 15 yards left.