Posture Do's and Don'ts
The video pretty much says it all but here are a few errors I see on the range matt that you will want to avoid.
Excessive Anterior Tilt
This is tilting the pelvis too much so that there is an unnatural amount of arch in the lower back. Aim to keep your spine in its neutral curve.
Curvature in the Upper Back
As we extend our arms to grip the club it is easy to round off the shoulders and 'compress' the chest; leading to swing restrictions. Aim to keep your chest out and proud and your arms will hang either side of your ribcage and not on top of your pecs.
Width of Stance
Too wide a stance will restrict your rotation and counter to popular belief, it often leads to instability. For irons, keep the outside of your shoes in line with the outside of your shoulder line. With the woods, aim to have the middle of your laces under the outer edge of your shoes.
Your weight needs to be evenly distributed between the feet and between the heel and the ball of the foot. It is ok to favour the ball slightly but if you find that your toes are 'grabbing' the ground to keep you upright then you have gone too far.
This needs to be a position of readiness from which you feel powerful and confident. If you are having to think about it excessively or feel self-conscious then you haven't put enough time in on the range. Rehearsing this area of your set up is easily done in front of a mirror and will pay dividends.