Dobermans, a lean, medium to large sized breed, are very smart and extremely energetic. They are loyal and affectionate "people dogs" that need to be with their families, and they love human interaction. Dobermans are also wonderful guard dogs that protect their families them aware of danger. This protectiveness can often cause the dogs to become obsessive barkers. The barking, however, can be addressed and curbed through patient, consistent training.
Exercise your dog. The doberman is a highly energetic dog. Barking is often a symptom of boredom and lack of exercise. Dobermans have a high energy need and require daily (or more) walks and time to run freely in a safe environment. Make sure that your doberman gets adequate exercise.
Teach your doberman to speak. Your dog will naturally want to alert you to certain things, like a person knocking at the door. You do not want to train your doberman to stop this behavior completely. Have a partner help you by standing outside and knocking or ringing the doorbell. When your doberman barks, stop him or her after two or three barks and say whatever phrase you want to use to signal the dog to stop barking. "Good bark" is a good one or the word "quiet." Give the dog a treat so that he or she associates barking only once or twice as a good thing.
Ignore your dog. When crating or otherwise containing your doberman, he or she may bark to try to get your attention. You cannot give in while the dog is displaying this behavior. Make sure that your doberman has clean water and food and is otherwise taken care of, then leave him or her in an appropriate comfortable enclosure. If you must go in to check on the dog, wait until he or she has stopped barking and praise the dog for being quiet. Going in while your doberman is barking is a sure way to encourage him or her to continue to bark longer and longer.
Practice your training frequently and consistently. Your dog will not learn nor retain any important commands after only one session, nor even after a few. It takes consistent and patient training to teach a doberman to not bark, and continuous practice to help the dog retain the knowledge and commands.