Dogs are limited in their ability to communicate, so they often resort to using growls to let you know they are in pain, angry, frightened or grouchy. Regardless of the reason your dog is growling, it is often the precursor to biting, so take the growls seriously and put a stop to the noise. While it is important for your dog to respect you and not intimidate you with his growls, don't stick your hands or face in the face of a growling dog.
Determine why he is growling. Dogs growl when they feel threatened, if they are in pain and to guard food and resources. if you are grooming your dog and he growls as you move down his back, he may be in pain. If he growls while you are walking by his food dish, he is guarding his food.
Modify his lifestyle. A visit to the vet can help you determine if your pet is in pain. If he growls because he feels threatened, rethink how you approach him. Call him to you, rather than walking to him. Crouch down and pet him rather than leaning over top of him. If he is guarding resources, you need to teach him that everything good comes from you. To do this, make it a habit of dropping a treat while walking by his food dish or the spot where he's lying with his toy. Keep walking, and don't say anything. Go back and forth, dropping treats, until he quits worrying about you taking his food or toy and looks for you to drop him a treat.
Add obedience training, if you are not engaged in it already. Obedience training teaches your dog to listen to and focus on you and enhances bonding.
Consider removing privileges. If your dog consistently has one toy or area of the home that he guards, you may need to take the toy away or block him from that area. Use this as a last resort, if he continues to growl after obedience training and flooding him with treats.