Kim, ditto all of the above but the "grab him by the throat" as well as shaking advice.

As you are probably aware, "mouthing" is another form of doggie interaction and there is a distinct difference between playful nipping and a focused bite.

We have Golden Retreivers; with a new pup and their insistence on play we begin training heel, sit, stay and come on the lead for a 15 minute playtime before each puppy meal. And you can start now. Its a game, he gets fed and learns his manners (a must in what will obviously be a big dog!).

Have fun! You need to post pics.

Ed