Milton Erickson developed a unique method for hypnotherapy, in which the patient is "permitted" to enter a trance, and the therapist accompanies the patient. By first agreeing with the patient in their current behavior and then making small alterations, the therapist enables the patient to work toward a new set of behaviors and beliefs.
Here's Erickson inducing a trance using the "levitating arm" method. Fascinating to watch.
More: part 2, 3, 4, 5