This is a comprehensive look at what is known about the different types of acupuncture point stimulation.  A very nice reference article to have, and has free access to the article online.

 

Factors contributing to therapeutic effects evaluated in acupuncture clinical trials.
Shi GX, Yang XM, Liu CZ, Wang LP.
Trials. 2012 Apr 21;13(1):42.
Abstract

ABSTRACT: Acupuncture treatment has been widely used for many conditions, while results of the increasing numbers of randomized trials and systematic reviews remain controversial. Acupuncture is a complex intervention of both specific and non-specific factors associated with therapeutic benefit. Apart from needle insertion, issues such as needling sensation, psychological factors, acupoint specificity, acupuncture manipulation, and needle duration also have relevant influences on the therapeutic effects of acupuncture. Taking these factors into consideration would have considerable implications for the design and interpretation of clinical trials.