Student response systems can help instructors integrate active learning into their classrooms. Such technology is known by a variety of names, including classroom response systems, student response systems, audience response systems, electronic response systems, personal response systems, zappers, and clickers. The "system" consists of three components: (1) a clicker; (2) a receiver; and (3) software. Each student possesses a "clicker"--a personal handheld keypad that allows them to answer multiple-choice questions posed by a course instructor. Students choose their answers by pushing the appropriate numbered button on the clicker, which transmits a radio frequency signal to a "receiver." This receiver collects the data that the class clicks in and sends it to the clicker "software" installed on the instructor's computer. The instructor can then display a "class response histogram" to the class as an object of discussion--especially in instances where there is no consensus among students as to the correct answer. For the purposes of simplicity and consistency, the authors refer to the entire system as "clickers." They tested three different clicker implementation approaches from 2008-2009: (1) the "students-pay-without-incentive" (SPWOI) approach--students bought clickers and were not awarded grade points for clicker use; (2) the "students-pay-with-incentive" (SPWI) approach--students bought clickers, and three to five percent of their final course grade was based on clicker use; and (3) the "institution-pays-clicker-kit" (IPCK) approach--instructors loaned students institution-owned clickers on a class-by-class basis. In this article, the authors discuss these models and provide a decision tree that can further serve as a guide in clicker implementation. (Contains 4 figures, 1 table and 13 endnotes.)