I found this somewhere, and you gotta understand that proper growling is much harder than most people perceive it to be
"The 'magic technique' you hear being thrown around in the talks of growling actually refers to a technique in actual singing called the diaphragm push. It is also referred to as "growling for your gut" or "growling from your stomach". What you want to do is first develop your lungs. Let me give an example of an exercise that will help you develop your lungs. NEVER BREATHE IN THROUGH YOUR NOSE.
Ex. 1 -
Open your mouth into the shape of an O. Keep your throat open and relaxed. You should not feel tension in your throat during this exercise. Place your hand in front of the opening of your mouth. Position your parallel to your face as if you were about to judo chop your nose with the index finger side of your hand. Bring your hand closer to your face and make sure there is contact between your face and hand. Breathe in slowly but taking in air as much air as you can at a steady rate. NEVER BREATHE IN THROUGH YOUR NOSE. Your chest should not come out. When you are taking in air your stomach area should come out and your shoulders should not rise. If you feel pain you are doing it wrong. Now extend your arm away from you with your palm facing you and your palm should be in a straight line and same level from your mouth. Blow out all your air. If you do not feel the air hitting your palm you are not blowing out hard enough. After you get this slow proceed to doing it faster. It would help to do this in counts. In for 4 counts then out for 4 counts, Then 3/4, 2/4, 1/4. 3/3, 2/3, 1/3, 2/2, 1/2, 1/1.
Doing that exercise will increase your lung capcity and help greatly in your vocal work. Now how do you apply that to growling? Well try to growl first. Notice what your face is doing, and what your throat and body is doing. You want to keep the O shape in your mouth. Make sure your throat is relaxed and not tensed or you will not get a low sound. Make sure your body is not tense. When growling make sure your shoulders do not rise not does your chest come out. You stomach is what should push out. Now onto the diaphragm push.
Diaphragm push -
The diaphragm push is basically the combining of all these techniques. When you are growling make sure you push your stomach out and you and not using your throat to generate the sound. You should hardly feel any pain if any at all. You might feel light headed at first getting used to pushing that much air. The key is to push much as much air as you can. The more air, the bigger and fuller the sound. This is why you need to do lung exercises. Keeping your mouth in the O shape and making your throat relaxed is the key to getting a dark, rich sound. Another thing you might want to try is dropping your jaw. The closer you keep your jaw together, the more pinched and bright sound you will have. So you want to try to seperate your teeth when growling. Adjust the distance to fit how you want to sound.
When you growl make sure you growl at a volume where other people could hear it. If you can hardly hear your growls then that means you are not pushing air and need to reconsider your technique. Air blowing does not mean volume though. The more air you blow and relaxed and open your mouth is, the better sound you will attain at a good volume."
