@forteller there's a lot of good points in the other comments. Some addenda:
Which vs. what - which implies there are several options applicable to the situation, what implies there's just one. But that's not a strict convention.
Alternates for "refrain from" depend a lot on the degree of personal volition involved in not being a werewolf.
Degree of formality is important. "Refrain from passing gas on the aeroplane" is more formal than "don't fart on the plane", with the same meaning.