The most important part of our golf swing is our setup. Our swing will be determined by the way we set up our body.
As we setup, our spine must be positioned at 90 degrees to the lie angle of the club and should be straight. If the spine is bent or out of position at address it will be difficult to rotate properly. For example, if a hinge on a door is bent it is difficult to open or close the door.
If we are standing up too straight at address our swing will tend to come over the top of the golf ball. If we are bent over too much, our swing will come too much from the inside of the golf ball.
By positioning the spine correctly in our setup, we will be able to create a swing where our power turns into the golf ball.
We also want our arms to hang straight from our shoulders. If we are reaching too much, our swing will tend to get inside too quickly and if our arms are too close to our body, our swing will start to the outside. The left side of the body should also be a little higher than the right side because our left hand is higher on the club for right hand players.
Work on this proper setup and you will find that it will much easier to swing the club on the correct path and rotate the shoulders properly.