It’s good for your game
Aim, then align
Whatever else golf is, it's a game of geometry. Lines and angles on a four-dimensional playing field relate the golfer, the ball and the target.
The mistake I see most in my teaching is a faulty setup, and that is like beginning a trip by heading in the wrong direction. The first step to a perfect setup is to aim your clubface correctly, and the second is to align your body, and always in that order -- aim, then align.
Because it's your clubface that makes contact with the ball, where it's pointing at impact determines the direction the golf ball will initially travel. It's helpful to use the lines on the toe and heel formed by the grooves on your clubface for aiming.
It may sound simplistic, but you must take great care to aim your clubface at the target at address because that's where you want it looking at impact. Always set the clubface behind the ball before you take the rest of your set up. Then build your stance around your clubface so that if you extended a line from the leading edge (the bottom part) of the clubface to your toe line, the two lines would be perpendicular.
Your shoulders determine the direction your arms swing, so they must be aligned correctly to ensure that your clubface looks at the target at impact. They should be parallel to the target line because, biomechanically, your arms swing in the direction that your shoulders point. When you're aligned to the right, if you make a good swing, your swing path will be too much inside-to-outside of the target line.
The alignment of your hips is important because your hips dictate the amount of rotation away from and back to the ball. Open hips (facing more toward the target than strictly parallel to the target line) cause you to underturn on the backswing. If your hips are closed at address (lined up facing away from the target), you run the risk of overturning on the backswing and then not being able to get your hips turned back in time for impact.
To make sure your aim and alignment are correct, lay down two clubs to help you judge your position, one along your foot line parallel to the target line and one behind the ball on the target line. When your body is parallel with the target line, it's said to be "square" to the target. When your clubface points at the target, it is also square. Begin from a perfectly square stance and then make adjustments based on your flexibility and body shape.
Tomasi writes for Universal UClick.