Striking the ball with the clubface open to the swing path imparts a sidespin to the golf ball causing the slice. The following are the major faults that cause an open clubface:

• Failure to release. The blade of the club is held back from rotating (releasing) by the hands/arms. If the left wrist bends, it becomes almost impossible to release (roll the arms over) properly during the swing.
• Too tight a grip. Gripping too tightly can inhibit the release (rolling over of the arms at impact) also. Keep the grip pressure light but firm. A too tight grip can prevent the wrists hinging properly.
• Open clubface at address. The opening of the clubface can just be carelessness in not addressing the ball with the clubface square. Your setup can cause you to open the clubface. A forward press that is a little too hard can cause the clubface to open. Also, a stiff right arm will cause the clubface to open. If you start your swing from an address position with the clubface open it.s very difficult to get the clubface square again before impact.
• Playing the ball too far back in your stance. Playing the ball too far back in your stance can make you hood (close) the clubface reducing the loft. The reduction of loft will make a slice more likely. The rearward position can also make it very difficult for you to get the clubface closed before impact. This can result in a push slice.
• Weak grip. The position of your hands on the club at address can effect the clubface position at impact. Quite often golfers grip the club too much to the left (weak grip). Make sure your hands, especially your left hand, are not too far to the left - toward the target- because the clubface can be turned open too much during the swing. Review the grip diagrams in Step Two.
• Handsy takeaway. The takeaway should be more of a one-piece move with the rotation of your shoulders leading your arms along a path to the inside and up to the top of the backswing. A handsy takeaway can cause the club to go to the outside leading to an outside-to-inside swing path.
• Overswinging and losing the proper grip on the club. Swinging too hard can cause you to regrip at the top of the swing. This can cause the clubface to open.
• Pulling with the left arm. Strong pulling with the left arm can cause you to get your body and hands in front of the ball at impact, leaving the clubface open. Swing through with both hands working together to get that clubface square at impact.
• Starting the downswing with the shoulders as opposed to the legs, hips, hands and arms, will most likely have the shoulders turned too far past square at impact. If the shoulders are turned to the left at impact the swing path is almost surely going left also.
• A collapsing left arm will make it unlikely you.ll get the clubface square at impact. Most golfers are right-handed so their right arms are stronger, more coordinated and therefore dominant. At impact the arms should form a .V,. but a dominant right arm can push the left arm out of the way causing it to collapse (bend).
• Flying right elbow. The elbow can be away from the body on the backswing. Jack Nicklaus does it. But on your downswing the right elbow must return to the right side.
• A too narrow stance. A narrow stance encourages a steep downswing. While this is OK for iron shots, hitting down on the ball on a drive, will encourage an outside-to-inside swing causing a slice.
• An incomplete shoulder turn. Your shoulders and hips should turn enough to coil and create tension on the backswing. If they don.t, in order to hit the ball hard enough, you may wind up hitting too much with the hands and arms. This arm dominated movement prevents a normal release.
  written by Joe Davidson www.SimpleGolf.com