Ideally, one would have time to plant the seed of doubt long before any sharp instruments became involved.

[She answers as though this should be obvious; she's had certain truths drilled into her from an early age, having been taught about these very particular subjects when most children would have been practicing their arithmetic.]

Psychological torture is not to be underestimated. If one can get their subject to do the heavy lifting for them, once pain is introduced, they simply fall to pieces. Of course, having that sort of opportunity can be a luxury. In that case, you want the pain to be approaching unbearable, but not so much that your subject's mind becomes addled. I've found heat to be especially effective.

[Humans and vampires alike fear fire, and for good reason.]