Socialization is easy, fun and will bring you and your dog closer for all the new experiences you will share together. GSD's seem so smart it's scary sometimes. But you have to feed them the right information and feed it in a consistent manner so they don't get confused. If you want a dog to behave in a friendly manner towards children, strangers and other dogs, then you have to expose them to these situations often and consistently as they mature and let them define these experiences in their territory. This is easy to do if you start with a pup. Take your dog everywhere you can during your daily routines. Let them smell strange new smells. Meet strange new people. Get acquainted with any and all sorts of loud and strange noises. All this serves to desensitize your dog and makes them more ready to accept all the sorts of odd phenomenon that takes place in your life as a matter of course. If you saturate your pup's life with this kind of training, you should have no problem acquainting your dog with new people, and should be able to take a walk in the park with your dog and not have to worry about them biting a passerby. Of course there are exceptions to every rule. Some dogs, through inadvisable breeding practices or simply genetic accident, will be uncontrollably paranoid and aggressive. Care when selecting a pup can often eliminate the chances of ending up with a mentally defective dog. In my experience, crazy dogs are rare. I believe nurture (a dog's training and environment) plays a somewhat greater role in canine behavior than nature (a dog's genetics).
The process of socialization will also help facilitate basic obedience training, such as walking well on a lead