The acquisition of factual knowledge is increasingly insufficient to prepare students to cope in this complex and rapidly changing world. Students need to learn effective ways of thinking so they can use their acquired knowledge flexibly, solve diverse problems, and become good independent learners. Two pervasive educational problems limit the possible efficacy of any instruction: (1) lack of individual guidance and feedback; and (2) deficiencies of basic cognitive functions. A computer-implemented reciprocal-teaching strategy can help students learn important cognitive abilities. A prototype computer tutorial was designed to teach college students Newton's second law of motion, a principle taught in every basic physics course and one with which students often have difficulty. In the basic implementation tutorials, PAL (the computer used as Personal Assistant for Learning) plays the role of a coach who makes decisions according to the methods suggested by the student, and then assesses and corrects the students' implementations. In the basic coaching tutorials, the roles of implementer and coach are reversed, with the student practicing how to make appropriate decisions and assessing PAL's implementation. The tutorial programs were tested in a pilot experiment in an introductory physics course for college science majors. Student volunteers (n=45) were divided into a PAL group, a tutoring group, and a control group for a homework assignment dealing with the application of Newton's laws. Students in the PAL and tutoring groups performed appreciably better than students in the control group. Students had very positive reactions to the PAL tutorials, and seem to have acquired a more explicit knowledge about relevant thinking processes from using the tutorials. Implications are discussed. (Contains 14 references.) (SWC)