Timing is a common word when discussing the golf swing, yet many players aren't quite sure what it means. They know it relates to coordinating all the movements that comprise the swing, but that doesn't explain what those specific movements are. I hope to clarify that in this article.
The golf swing is a combination of two distinct physical movements. One is body action and by body I mean the upper torso, hips and legs. This unit generates power by coiling and uncoiling. Maintaining an axis anchored at each end (by a steady head and anchoring your feet) you coil to the right on the backswing, then uncoil to the left and the downswing.
The other unit is the arm, wrist and hand action that combined work as a swinging action, and supply some power to the shot. Their primary function, however is to transmit to the clubhead the much greater power generated by the winding and unwinding of the body.
A properly timed golf swing is one in which the coiling and uncoiling actions of the body mate perfectly with the swinging action of the arm, wrist and hand unit - to deliver the clubface squarely to the ball with maximum clubhead speed at the moment of impact. Once you understand how the body pivot and arm-and-hand action interrelate it becomes easier to diagnose and correct poor swing coordination. The way your shots fly tells you whether the two are in sync or not.
If you are slicing or topping shots you want to slow down you body unwind and increase the use of the clubhead by speeding up your arm swing. Think of swinging the clubhead down and through the ball before your shoulders unwind. The flight of the ball will tell you when you've struck a balance.
If you are hooking or hitting shots fat you have the opposite problem. Your arm and hand swing is ahead of your body unwind. To correct this speed up your leg and hip action relative to the movement of your arm, wrist and hand unit. Focus on starting your downswing by unwinding your left hip and keep it moving to the left while delaying your arm and hand swing. Solid, straight shots will tell you when you've got the correct balance.
There has always been debate as to playing golf with a "body" method or a "hands" method. As John Jacobs said is his book, Practical Golf , "The good golf swing is neither primarily body action nor primarily clubhead action: it is a perfect blend or balance of both. And the word for that is timing".