Many golfers have issues with their wrists during their golf swing. The most common issue is getting too wristy or flipping the club in the downswing and through impact which makes the club release too early. The common term associated with this problem is called casting.
Setting or hinging the golf club well in the backswing is the first step to getting your wrists to work correctly. In order to do this, it's important to have a correct grip where the club sits down in your fingers. You also want to have good grip pressure and keep the grip pressure the same throughout your entire swing. On a scale of 1-10, I recommend holding the club at about a 5 or 6. You want a secure grip but definitely don't want to create too much tension by gripping too tightly.
As you swing the club back on the backswing, the club will set as you hinge your wrists. The wrist hinge should typically happen in the first 2/3rds of the backswing. Once you've gotten to that point in the backswing, the club should be fully set and as you finish the backswing, you want to try and maintain the angle between you right forearm and the club shaft.
At the top of the swing, there should be approximately a 90 degree angle between your right forearm and the club shaft if you have set the club or hinged correctly. You want to feel that your wrists are firm at the top of the backswing. Then, as you make your downswing, feel that your wrists stay firm also. The whole downswing and follow through we want to keep the wrists feeling firm and focus on swinging the arms past the body and turning and finishing the follow through.
Golfers who flip their wrists or release the club too early will often not turn correctly. If you stop your body turn on the follow through, then the wrists will need to flip in order to compensate.
At impact, especially with the irons, the club shaft should lean towards the target and your hands will be slightly ahead of the ball. Holding the lag or angle of the club on the downswing and not flipping the wrists will help with coming into a good impact position and being able to compress the ball well. The club will release automatically and the wrists will unhinge slightly in the downswing. By feeling that the wrists stay firm when you swing down, the club will automatically release the correct amount. Feeling like you are using your wrists or flipping them will cause too much release with the club.
Let the wrists set and hinge correctly in the backswing and keep them feeling firm in the downswing and follow through and you'll be hitting better golf shots with more compression, distance, and consistency.