This paper attempts to organize, systematize, elaborate, and elucidate a number of basic principles for behavioral change that have experimental foundation. The two major areas discussed concern procedures and principles for strengthening and weakening behavior. Matters of inducing behavior are considered. Principles for strengthening behavior are grouped around post-response events (including reward), characteristics of the environmental situation and the task, and aspects of the organism involved. Principles for weakening behavior are classified by the basic methodologies employed. Several basic methodological points are described. (Author)