A calm and balanced manner of training is needed, as they are a very sensitive breed who will listen to the tone of your voice. (puppiesndogs.com)
But sensitive breeds such as German Shepherds need careful introductions to new people and places, and plenty of positive reinforcement for appropriate behavior, until 2 - 3 years of age. (germanshepherdcentral.net)
Additional material is suggested for more cold sensitive breeds, older dogs, or dogs with certain health concerns. (ourpals.com)