Remember your body language. Dogs are most sensitive to communication via eye contact, body language and tone of voice. So to assert your alpha position, keep your body higher than your dog's, and pat your dog on top of his head, not under the chin. Smile and make your eye contact soft and loving. Being alpha means you win.
Obedience training helps every behavior problem.
Practice obedience exercises at home daily and with a group weekly. Read books that stress positive, motivational methods . Seek professional help if you're stuck .