Released by the Freedom of Information Act. This document is a thorough description of how the CIA recommends interrogating a subject.
To get the information that is needed there is nothing withheld short of torture. For example in "Threats and Fears," the CIA authors note that "the threat of coercion usually weakens or destroys resistance more effectively than coercion itself. The threat to inflict pain, for example, can trigger fears more damaging than the immediate sensation of pain."
Under the subheading "Pain," the guidelines discuss the theories behind various thresholds of pain, and recommend that a subject's "resistance is likelier to be sapped by pain which he seems to inflict upon himself" such rather than by direct torture. The report suggests forcing the detainee to stand at attention for long periods of time. A section on sensory deprivations suggests imprisoning detainees in rooms without sensory stimuli of any kind, "in a cell which has no light," for example.