A lack of hands means that puppies have to use their mouths for much of their exploration and that can lead to nipping. Nipping and biting isn't done maliciously; it's usually playful, a puppy's way of relating to its people as it relate to fellow dogs. However, this nipping is unacceptable behavior and the sooner the puppy is taught that, the better.
Discourage nipping at fingers and feet by giving your puppy something that it should be chewing on. Keep a chew toy close at hand and when the puppy starts to show signs of nipping, give it a toy before it can latch onto any skin. Biting isn't necessarily a bad habit--chewing on rawhide and bones will help keep your puppy's teeth healthy and clean--but it has to be properly channeled.
Yelp. Your puppy isn't trying to hurt you, so let it know that that's what it's doing. A sharp yelp, like the noises made by other puppies, will send a clear message. Put on a show. Get up and walk away from your puppy. Dogs are pack animals and to be shunned by the pack leader sends a distinct and unmistakable message. Ignore the puppy until it has calmed down and then give it a chew toy.
For nipping that continues, don't be afraid to assert your authority over the puppy. Relating to the puppy on the same level as another dog can work to your benefit. Take the puppy by the scruff of its neck and push it gently away, saying, "No" firmly. Use the tone of your voice and body language to get your point across. A scruff-of-the-neck shake is how your puppy's mother would deal with an unruly pup and it's sure to get the message.
Play games with your puppy. A busy puppy is a happy puppy and every game of catch teaches acceptable behavior. Your puppy will soon learn what it can bite and what it cannot. Never let nipping during a game go overlooked.