An exceedingly high percentage of the women who play golf are slicers. They slice chiefly because they bring the club back with an incorrect shoulder turn. As they near the top of the backswing, instead of continuing to swing the club back and to turn the shoulders easily, they have a tendency to push their shoulders and arms up. Then, before they have completed the backswing, they start the downswing. Not only is their timing thrown off, but starting the club down from a position at the top where it points to the left side of the fairway is the invariable prelude to coming into the ball from the outside and cutting across it—slicing.
At the top of the backswing, the club, ideally, should be directly parallel to your intended line of flight, pointing, as it were, right at the target. If you have made a sufficient turn, your shoulders will be square. One excess, of course, is as bad as the other, and I would caution you about over-turning the shoulders. This places the club in a position at the top where it is pointing to the right side of the fairway. A hooked shot generally results, for if you overturn going back, you have to over-turn to get back to the ball.
from BETSY RAWLS, Country Club of Spartanburg, S.C.