Wrist set is a vital part of your backswing. You develop clubhead speed in part because your wrists uncock during the downswing, and you certainly can't uncock them if you don't set them first. Although it's a simple action, many players struggle with it. You need to recognize that your wrists are already partially set merely by addressing the ball. At address, the club shaft is automatically set at an angle between 45 and 60 degrees to your forearms. You create the rest of the angle during your backswing. There are two types of wrist set. The classic method is called a "late set" or "late cock," where the wrists don't set fully until your hands reach the top of your backswing. The modern method is the "early set" or "early cock," where the wrists finish their set just above waist high in the backswing. Both can work equally well, but most players find they prefer one or the other.
Address the ball normally. Bend from the hips, knees flexed slightly, with your weight over the balls of your feet. Let your arms hang down naturally, with the upper arms resting lightly against your chest. Hold the club with your normal golf grip; if you dangled a plumb line from your lips, it would hit your hands.
Make a one-piece takeaway. Although there's a lot of confusion around this term, all it means is that you begin your backswing by turning your shoulders first. This shoulder turn, sometimes called a "coil," allows your arms to stay reasonably straight without locking your elbows. You want your arms and upper body to stay as relaxed as you can.
Turn your shoulders until your left arm -- your right arm if you play left-handed -- is parallel to your target line and your hands are about waist high. Your elbows should still be fairly straight and you will have completed most of your shoulder turn. As a rough reference point, your left shoulder should be nearly under your left eye. At this point, your wrist angle will appear almost the same as it was at address.
Pivot your arms up with the shoulder joints. Your right elbow will move slightly away from your side. With a late set like this, you want your elbows to stay mostly straight until your hands are just below your shoulders.
Let your right elbow begin to bend -- your left elbow if you're left-handed -- while your left elbow remains extended. This is where many players get confused. Your wrists will set in reaction to your elbow bending. As your elbow bend increases, so will your wrist set. Your wrists will finish setting when you reach the top of your backswing and your elbow stops bending.
Follow steps 1, 2, and 3 of the "late-set" instructions. This will put your hands around waist high with both elbows extended and your shoulder turn mostly completed.
Start bending your right elbow -- your left elbow if you're left-handed -- while your left elbow remains extended. This is where the early set differs from the late set. Because your elbow starts bending earlier, your wrists begin to set earlier. By the time your extended left arm is parallel to the ground, your wrists will have finished setting and your right elbow will still be fairly close to your side.
Pivot your arms upward with your shoulder joints until you reach the top of your backswing.