Commit yourself (and your family) to training your puppy. Use the resources of formal class training beginning from about 12 weeks of age with a puppy kindergarten class for socialization and early training.
Move on to more formally structured classes when the pup is six months old. Do your homework. Being intelligent and motivated, an untrained or ill-trained GSD can prove to be an unacceptable family member.
Work on subordination and relaxation exercises every day.

Be wary of asking too much physically from a young GSD pup, such as jumping, long runs, etc. While your pup is growing, you can damage the growth plates or exacerbate a tendency to hip dysplasia. Your puppy should be 12-18 months old before any heavy physical demands are placed on it.

By 10 weeks of age, your GSD puppy will weigh somewhere around 13-20 pounds (depending on sex and bloodlines). A GSD will continue to fill out until 24-36 months old, but should reach close to full adult height by 12 months.

Your new GSD puppy will require a great deal of attention and socialization. Between 4-12 months, GSDs can be prone to "adolescent shyness". If the dog is well-socialized during prior to this point, you can minimize many of the worries that are associated with a shy dog. Puppy Kindergarten and obedience classes are highly recommended for all dogs, but especially for larger breeds such as the GSD. Expose your puppy to as many different experiences as possible, but do not allow your puppy to be traumatized.

Although it is very tempting to pet your GSD puppies ears backwards away from the nose, it is preferable to not do so until the musculature in the ear is fully developed and the ear standing erect. Be content with scratching the ear at the base where it meets the skull. Your puppy will probably find this very enjoyable
anyway.

And don't forget how important puppy immunizations are!