Everything you read and are told by the professionals is **NOT** to bite back. My oldest (now a 14 year old, HS Freshmen honor student, athlete, musician and all around "good kid") bit and we tried **EVERYTHING** from reasoning/sympathy to ignoring the behavior to having her bite on a lemon as "punishment". Nothing worked.
... that is until I bit her back. Not hard, but it got her attention. She bit me after a "kiss", and I just gave her a little "nip".
And then when she entered pre-school at the tender age of 2 1/2, she was bitten by a little boy. That became the prime opportunity for us to have "The Talk" about how much she was hurt by being bit and how she was hurting others (including me!) when **she** bit.
... and she turned out alright... (...at least so far...)
Sorry, but we tried everything else...