As far as I saw you really just go off a tiny bit of guesswork and hope you're right. But then I've only played the Vongeo disaster.
And I'm pretty sure there's a foolproof way to find out who's a wolf if all the villagers cooperated, but it'd be pretty cheap.
Typically, there'll be some small clue a day or two in (game time). It might be a red herring, but there'll be something to hint at someone who might be a wolf. Sometimes it'll come from the psychic, or it might be a slip of the tongue from a wolf, or a hunch based on wolf attack patterns, but it'll come.
Then, only then, will I support a lynch. Otherwise, as I've said, we're shooting ourselves in the foot by making a random selection from a group of two dozen villagers and three wolves.