When your dog growls, it means he’s got stinkin’ thinkin’! Some trainers say ignore the growl, because at least you’ll know when the dog is going to bite.  That’s wrong!  You must correct growling so the dog never thinks about the next level, which is a bite. 

The best form of correction is with an Ecollar, because you can safely stop growling from a distance, without putting yourself in harm’s way.  By the way, a dog who has experienced a meaningful consequence is more likely to stop practicing stinkin’ thinkin’.