We always just said "no bite!" and walked away/turned away/ignored for a couple minutes. Puppy quickly learned that a bite results in no more play, no more petting or attention.
Also practiced with a treat in an enclosed fist, offer it to the puppy and when he bites say "no bite" until he licks you instead, then give the treat. This worked for us but I imagine does not always work.
Also, "no bite" with a redirect to a toy then praise helped. We did all of these things together and they helped our first pup who was very mouthy!!! Good luck!
Warden - Sable GSD 4/23/2013
Blackjack - Black and tan GSD 4/23/11-6/1/2012