Throughout the entire swing you should let your body swing your arms, much like swinging a heavy ball at the end of a chain. If you keep your elbows together and in front of your center (the upper part of your body) in the hitting area centrifugal force will create club head speed.
The faster you can move the body in the forward swing without sacrificing a smooth rhythmic tempo the more club head speed you will develop. The left arm will rotate and the right arm will extend and cross over the left, just as a home run hitter’s arms react.
It is imperative that you keep the body moving to the finish. Otherwise the arms and hands will deliver prematurely.