How do you create rotation on a bowling ball? First, two things. One, you have to have the proper fit and grip. And you also have to relax and allow your swing to come through while you're performing your approach. As you're relaxing in your approach, you must have a relaxed grip.
Otherwise, your fingers and thumb will not come out of the ball the right way. You need to have your thumb come out first and then transfer the weight to your fingers. So in other words, you're going to allow your swing to come down on your downswing and properly release it with your thumb facing forward so you're thumb is sliding out. When the thumb slides out, it's going to transfer the ball weight into your fingers. When that happens, the rotation comes off the side of your hand and then creates rotation down the lane, which will give you a reaction into the pocket. By creating rotation, the ball will create more of a stronger angle to the pocket, create pin action, and you're going to be left with less splits and less spares.
The rotation comes from not only your smooth and relaxed arm swing, but you have to transfer the ball off your hand. Any major motion with your wrist could actually go against you and cause you to grip the ball differently. By allowing the ball to come down on your downswing, you have to make sure that thumb is relaxed, at the same time facing your target. When the rotation is created, your thumb comes out first and transfers to your fingers. When your fingers are in the ball last, that little bit left in the ball is going to give you rotation and create some reaction down the lane. The proper way of creating rotation is allowing your hand to fall or to collapse.
Getting the thumb out of the ball first is going to allow your hand to tilt, which in turn will transfer the weight into your fingers and create rotation. The one thing you want to stay away from doing is trying to grab the ball or help it or over-control the ball by turning your wrist or gripping it harder. By throwing harder, you're going to grip the ball even more, and it's going to deter your rotation. And that's how you create rotation on a ball.