Touch in psychotherapy : theory, research, and practice

Should a therapist ever shake hands with a client, or touch a client's hand or shoulder?

There are taboos against erotic touch in psychotherapy, for excellent reasons, but what about non-erotic touch?

These latter forms of physical contact are not explicitly taboo and they can be powerful forms of communication.

Research and clinical experience indicate that they can contribute to positive therapeutic change when used appropriately.

What, then, is appropriate use?