There are soooo many opinions regarding this matter. Take a look around the site for various techniques that you could use.
One thing is for certain; GSDs are "landsharks" and they all nip as pups. But, rest assured, they all outgrow it and sometimes you just have to weather the storm... heh.
Be sure to get your pup enrolled in some sort of puppy kindergarten. It's a great opportunity to both teach and learn from your new companion