It is never a good idea to allow a puppy to bite your feet. You may think this is cute and even a little funny when you first bring your puppy home, but you will quickly realise that the biting will only get worse if you allow it to continue. This is because your puppy gets the idea that biting is OK if it is allowed to do it.
Say "Ouch" very loudly when your puppy bites your feet. Make sure you use a voice that is high pitched. Think of the sound a dog would make if it got hurt. The object is to let the puppy know that what it did hurt you.
After you say "Ouch," leave the room. This will teach your puppy that the bite hurts and that no one will want to play with it if it continues the behaviour.
Repeat Steps 1 and 2 and be consistent. This means that you must follow the steps even if it is inconvenient for you. Dog training requires persistence.
Make sure that you say "Ouch" even if the bites don't hurt. If the puppy is biting softer it may be because it is starting to understand that it was hurting you before. The problem is that the puppy needs to know that it should never bite a human. So keep telling the puppy "Ouch" until it stops completely.
Be patient; puppies take longer to learn commands than dogs. Take your puppy to obedience school after it reaches 6 months of age. Obedience school will teach the puppy not to bite other puppies.