A growl is a dog's cry for help. It's your dog's way of telling you he can't tolerate a situation - as if he's saying, "I can't handle this, please get me out of here!"
Your first response when you hear your dog growl should be to calmly move him away from the situation, while you make a mental note of what you think may have triggered the growl. Make a graceful exit. If you act stressed you'll only add to his stress and make a bite more, not less, likely. Don't worry that removing him rewards his aggression; your first responsibility is to keep others safe and prevent him from biting.
If the growl was triggered by something you were doing, stop doing it.
Yes, your dog learned one tiny lesson about how to make you stop doing something he doesn't like, but you'll override that when you do lots of lessons about how that thing that made him uncomfortable makes really, really good stuff happen.
This is where counter-conditioning comes in. Your dog growls because he has a negative association with something - say he growls when you touch his paw. For some reason, he's convinced that having his paw touched is a bad thing. If you start by touching his knee, then feeding him a smidgen of chicken, and keep repeating that, he'll come to think that you touching his knee makes chicken happen. He'll want you to touch his leg so he gets a bit of chicken.
Note: Make sure your dog's discomfort with you touching his paw is not related to pain. If it hurts when you touch him there, counter-conditioning won't work. It's a good idea to get a full veterinary workup if there's any chance your dog's growling may be pain-related.
When you see him eagerly search for chicken when you touch his knee, you can move your hand lightly lower and touch there, until you get the same "Where's my chicken?!" response at the new spot. Gradually move closer and closer to his paw, until he's delighted to have you touch his foot - it makes chicken happen! Now practice with each foot, until he's uniformly delighted to have you touch all of them. Remember that the touch comes first, so it consistently predicts the imminent arrival of chicken.
Counter-conditioning and desensitization teaches the dog that it is rewarding to stay calm in the face of stress.
If at any time in the process - which could take days, weeks, or even months, depending on the dog and how well you apply the protocol - you see the dog's tension increase, you've moved too quickly. Back up a few inches to where he's comfortable being touched and start again. Or, there may be other stressors present that are increasing his tension. Do an environment check to be sure nothing else is happening that's adding to his stress. Have the rowdy grandkids leave the room, give him a little time to relax, and start again.
Remember, dogs can't tell us in words what's bothering them, but they can communicate a lot with their body language and canine vocal sounds. Pay attention to what your dog is telling you. Listen with heart and compassion. Be gentle when your dog tells you he needs help. Come to his rescue. ...Treasure his growl.