A correct and consistent posture lends itself to a consistent golf swing.
Posture refers to the alignment of the body as you stand over the ball and
bring the club to the address position.
To assume the correct posture, firstly adopt a box stance. This will place
your feet correctly in relation to the ball and align the body with the target.
Then place your shoulders, knees and feet in the same vertical plane
perpendicular to the ground by leaning over at the hips and slightly bending
the knees. Your back should always be kept straight. The body as a whole should
be neither crouched nor upright as the club is brought to address the ball;
shuffle forward or backwards as required. Note that your left shoulder will
naturally drop because of the position of the hands when taking up the grip.
Given that posture should be maintained, you stand further from or closer to
the ball depending on the length of club being played.
If your posture is incorrect then you will tend to produce slices and hooks.
Slices can be caused by standing too close to the ball. In this situation the
posture is too upright causing the ball to be attacked from out to in. This
produces a strike across the ball and imparts spin. Conversely hooks are caused
by standing too far from the ball. Here the posture is crouched and the ball is
attacked from in to out.
If you are sure that you have adopted the correct stance and are producing
wayward shots then it very likely that they are caused by poor posture. As
always, practice and a degree of experimentation on the range are required to
make correct posture second nature.