For example a tug or war game, a chew toy and or/ play fetch with a toy etc. If he is not interested in the toy and continues to nip skin/clothes etc then the owner should prize his jaws from him/her and place him in "time out" (crate with minimal stimulation) or leave the room very briefly until he is calm and try the game again. He should learn that the biting behaviour toward people is unacceptable but biting toys can be such fun!!
A time-out is a period of isolation to allow the pup to calm down, the period only needs to be 5-10 seconds and not for minutes, then re-enter the room or let the pup out of the crate and resume the previous activity. If the play-biting resumes then repeat the process until the unwanted behaviour no longer continues.
I would favour leaving the room instead of putting said pup into the crate. We wouldn’t want the pup to see the crate in a bad way. Crates should be viewed by the pup and used in a positive and not negative way i.e. not used for 'time out'. In addition if the pup views the crate in a negative way then a confrontation is likely to ensue when the owner tries to time-out pup in crate and this may result in the play – biting leading to an a aggressive display.