"Bowling a Googly can trick any batsman in the world. But to bowl it successfully you must get the basics right.
The grip for the Googly is exactly the same as the leg spinner, as you can see here. The Googly should be used as an element of surprise. The normal leg spinner will turn away from the batsman. But the Googly will turn into the batsman like an off spinner and catch the batsman unawares.
The same principles of leg spin apply to bowling the Googly. Feet aligned straight. Weight going towards your target. And body rotation are all key. Use your front arm from a high position, keeping your elbow about shoulder height. The biggest difference though is that you will need to drop your front side in order to allow you to change the angle of your wrist, as you can see here. The back of the hand must face forwards, towards the batsman, to allow you to spin the ball the other way.
On point of release remember to pivot on the front leg to get the momentum in to your rotation. The target area you should be looking to bowl is just outside the off stump, so you can spin the ball back to hit the stumps. The Googly will take some time to master, no mistake, but with practice you will become more accurate."