L.W.
some babies are very interactive, and find the firm "no!" or other reactions entertaining - they don't understand that they hurt you!
other babies are *very* sensitive (some can be both) and a flick on the cheek can be enough to send these babies into a nursing strike - not to mention it starts you down the road of "violence begets violence" rather than modeling for your child what you expect from an early age.
with these babies who laugh when told no, and really for all babies - my first recommendation for biting would be:
1) have a teething toy - the SAME one - that you *always* have with you when nursing.
2) watch your baby carefully to assess when the biting happens - is it to signify the end of a feeding? is it when you are distracted and it is an attempt to connect/engage with you? is it to illicit another milk ejection (let down)? is it because baby wants to switch sides? is it teething discomfort?
3) when you figure out the pattern (if there is one) then BE PROACTIVE - watch baby closely, especially during that point in the feeding, and when baby "slips" down to the nipple, or the jaw tenses, or position changes - or baby gets that playful "glint" in the eye, unlatch baby and hand the teething toy, saying - "bite this - this is for biting - not mama" or something like this.
4) if baby manages to bite you (you miss the cue) do the same thing with the toy.
consistency with this approach usually works quite quickly, and biting is usually a passing phase anyhow.
if you do set the baby down, do so without the loud "NO!" but i would suggest the above process instead of setting baby down - it is much more connected to the real need that baby is expressing - much more responsive, rather than punitive. baby isn't trying to hurt you!