When it comes to the backswing, "turn" is a bad word, says Golf Digest Teaching Professional David Leadbetter (@davidleadbetter). It leaves golfers with the impression that all they have to do is take the club back with their bodies and arms and they've made good backswing. "I like to think of the backswing as coiling or winding instead of turning," Leadbetter says. "The idea is that you want to generate some energy and store it for the hit. You can't do that if you simply turn off the ball."
A good visual to understand what he's saying can be seen here. When he winds off the ball, the stretch band is nice and taught. When he turns off the ball, there's slack—in other words, very little energy has been generated.
From a swing-mechanics standpoint, Leadbetter says the core muscles should initiate the backswing. The chest and the big back muscles should feel as if they are twisting and torquing as they coil over the right leg. You should sense some pressure building in the right leg, too. Although the hips also will turn back, they shouldn't turn nearly as much as the upper body. It depends on your level of flexibility, but the hips should only turn about half the distance as the shoulders. The length of the backswing isn't nearly as important as having that wound feeling when you reach the top.
In between working on this winding action on the range, you can also help your cause in the gym with this easy dumbbell exercise. Click on the video to see me demonstrate it.