So far from what I have learnt from a website I go to, is never like Michelle said.. dont physically correct your German Shepherd. Treats work very well. I have a two year old black shepherd. We purchased her at a Rescue program. She isnt to fond of strangers and we take treats with us when we walk her to keep her mind off people walking by. Even a toy will work fine too. So when your puppy goes to nip at you, get her toy and take her mind off nipping you. I go to an awesome site:
http://www.torontogsdrescue.org/
They speacialize in German Shepherds and I am getting some really good support there.
Give your pup some treats when she has stopped nipping you and praise her.

Sandi