1. The Exaggerated Twist: most people erroneously believe that the more they turn their backswing, the more they will be able to gain distance.
Actually, to gain distance you should find the perfect posture and perform a fluid swing that will ensure a solid contact with the ball. On the contrary, by exaggerating the twist in the backswing, you will go out of the "ideal" swing plane, hence, you will need quite some compensation to strike the ball correctly, see picture 1 below: