There are numerous backswing issues that can affect your impact. For hooking, the two basic flaws are a backswing that is going too much inside or around, or a counter-clockwise twist of the shaft, or both.
If your backswsing is too much to the inside and not enough up, then the club is going to approach the ball on an angle that is too shallow and too much on the inside. In other words, too much along the ground. This swing direction will be a big part of spinning the ball counter-clockwise.
To fix this issue, take a look at your backswing at the top. Make sure the shaft is over your shoulder at the top, not too much behind you. To achieve this position, you may have to feel like the club is swinging a bit more up. You should also feel like your head is steady in the backstroke. No moving off the ball to the right! This will also make that backswing too flat and too much to the inside.
The next important element of the backswing is the clubface position. One of the biggest mistakes made by golfers who hook the ball is to turn the club counter-clockwise to begin the backswing. Unfortunately, this closing of the club simply creates a closed face at impact. The clubface should "open" on the backswing, relative to the target line. However, this natural opening is done with the turning of the shoulders and torso, not because of a twist in the hands.
When you are making your backstroke, just hold on to the club. No effort to twist or hinge the wrists should be made. When you get to the top, you can check for the proper position by looking at your left wrist. You should be able to lay a ruler underneath the face of your wristwatch and have it touch both your arm, and the back of your hand. In other words, the back of your left wrist should be straight.
With a good grip and stance, as well as a good backswing position, I'd be surprised if your hook is still here. If these first few areas check out, you're 90-percent of the way to curing your hook.
To begin the downswing, make sure you start down with a weight shift to the front foot and a turn of your body. While you are moving in this fashion, make sure you are tension-free in your hands and arms. This movement will virtually guarantee that the club is coming from the right direction.
If the ball still has a tail to the left, you can add this sensation: Try to get the feeling that the club is closing a bit too late. Feel as though the club is dragging across the ball with an open clubface. This should be done through softness in the wrists, with a feeling of letting the club swing. Some practice should give you the feeling.
The good news about working on this, or any other problem for that matter, is that you already have the best teacher in the world with you: namely, the ball. The way the ball flies gives you objective feedback about your swing.
You'll want to remember that you are improving if your 30-yard hook is now a 15-yard hook. No matter how strange a new move feels, always listen to what the ball tells you. You may be sure that the clubhead is staying open longer, but if the ball is still turning left, then you'll have to feel the club close later still. Not until you curve the ball to the right have you closed the clubface too late! The feel can trick you, but the ball won't.
Video: How to correct a hook