How do werewolves turn humans into werewolves?

Werewolves transform on the full moon every month. Different than animaguses, they do not remember who they are and who they love when they transform, but become savage beasts. When a werewolf bites a human while in its transformed state the human becomes a werewolf. If, like Fenrir Greyback, a werewolf bites humans while not transformed, the human will not become a werewolf, but may develop a fondness for raw meat. Generally, though, werewolves are normal people apart from their "furry little problems." :)

unless you mean in twilight or something, in which case whenever the hell they want.