Full extension in the backswing and release is definitely something upon which I'm still working. I have a bit of "flippy wrists" and "collapsing arms" remaining in my swing due to my beginning golf instincts that I need to overcome.
Of course, the best way to help extension and thus width is to extend on the backswing by pushing the club as far away from you as possible using the right arm; this will also help increase distance and help with thin and fat shots, as the left arm will be fully extended coming down.
Part of making extension work is keeping the head behind the ball at impact; I have a bad habit of drifting past it, which contributes to the wrist flip release and loss of distance.
The ball focus should be on the inside of the ball (not the top), as if you're trying to hit it to right field. Finally, the club should be moving it's fastest about two feet past the ball, so this means one must accelerate through the ball (not accelerate AT the ball). As a matter of fact, a neat trick is to imagine that you're hitting 3 balls in a row starting with the first ball (the real one); this will encourage extension through the shot. Do this for irons and woods!
It is so critical to feel like you’re behind the ball at impact. Your goal to improve golf driving distance will not happen if you don’t do this. Most of us get ahead of it and end up throwing the club at the ball, instead of driving through it and getting a full extension like the pro’s get. Staying behind it is the ONLY way to achieve that full extension and maximum power through impact.
Overswinging and power loss occur when you collapse your elbows on the way to the top, which drops your hands toward your head. Instead, maintain a firm left arm and try to keep your hands as far away from your head as possible to create maximum width.
Golfers who move their swing center in front of the ball at impact will always raise up their spine at impact. So keep your swing center behind the ball at the point of contact.
The greater width you have in your backswing, the bigger your swing arc will be. This increased swing arc will give your swing more time to increase your club-head speed as you strike the ball. More speed means more power, which equates to increased distance. To increase width, you need to increase the spacing between your right hand and right shoulder (right-handed golfers) during your backswing. Practice taking a backswing holding the golf club with just your right hand. Keep your right hand as far away from your body as possible during these practice swings. During this drill, reach your right hand toward the sky at the top of the backswing.
Rotational force is the most important fundamental of power. The more you extend your arms during the backswing and the longer they remain extended in the downswing, the farther you'll hit the ball. Watch Tiger Woods: He does this brilliantly, creating tremendous width in the backswing to set up a powerful arm swing through the ball.
As you start the club back, focus on extending your right hand away from the target, keeping the right wrist firm. This should prevent the right arm from collapsing and thereby narrowing the swing arc. This way, you create leverage on the backswing and store power for the downswing.
A good way to keep width in the backswing is to feel the right arm pushing away from your chest, not the left.