With all the dogs we've ever owned, when they are nippy puppies we put our thumb in their mouth and hold their bottom chin (thumb goes under tongue) and tell them firmly no biting.  We don't hold long and certainly not hard, but enough to get their attention.  This has always worked very quickly.. We also use this in conjunction with the loud yelp when they do bite.

Of course.. many may not agree with that.. but it works for us.

Our vet told us that dogs can be very mouthy up to a year old! We thought there was no hope! But as soon as Millie gets nippy we have come to realize its her way of telling us she is tired. We bought this great toy from our local pet store. Its a stages toy appropriate for her age and as soon as she gets nippy we put her in her bed and give her, her chewie and she is good to go.

Yelping when Bustelo nipped @ us really worked.  He's 6 month's & he's almost out of that stage.

With time, your puppy will stop.

Good luck!

What I've always done is, as the dog tries to nip or bite, grab its muzzle shut and give it a firm "no," then ignore it for a few minutes until it calms down.  Sometimes the pup will bite its tongue, which is no fun for it.  Eventually they learn that biting and nipping results in a bitten tongue and an angry parent.

Roxy, who is almost 3 months now, is very very nippy and if you tell her no or grab her mouth, she gets worse. We can't even hold her anymore without her biting us constantly. Right now we are trying the firm no and ignoring her when she bites, but it doesn't seem to work at all. I think I am going to try some kind of loud noise.