My husband and I had the very same problem - our Yorkie did nothing but bite and snap! It was so frustrating that I ended up in tears a few times because I thought we had an uncontollable and unruly dog and that we'd never be able to let people near him - he was THAT BAD. What really ended up calming him down was neutering (4 months old). Until then, what we found most effective was misting with water (not a stream - could injure eyes). The results werent great, but better than anything else we tried. Some of these tactics have worked for others:
1) Roll dog onto back and hold until he relaxes
2) Say ouch very loudly and retreat from play
3) Ignore the dog and refuse to play for a while after a bite
4) Bitter Apple spray can help
5) Some people bite back (SERIOUSLY) - I DO NOT recommend for your and the dogs safety
The above tactics did not work for me until our baby was neutered. 3 weeks later I noticed a sharp decrease in the number of times he would bite me. Also, if he did bite and I said "Ouch!" he seemed concerned rather than intrigued. So, there is a light at the end of the tunnel. As an FYI - it takes about 3 weeks to a month or so after being neutered for all the testosterone to leave their body, so you may not see him calm down for a few weeks (ours didnt). Take heart - I know that the problem is more frustrating than people realize!
