In today's diverse classrooms and age of accountability, teachers need to use efficient, research-based instructional approaches that engage all students, promote interest and variety in learning and teaching, and provide immediate and continuous informal assessment data. This article presents a rationale for using active involvement techniques, describes large- and small-group methods based on their documented effectiveness and applicability to K-12 classrooms, and illustrates their use in elementary and secondary classrooms. These approaches include ways of engaging students in large groups (e.g., unison responses, response cards, dry-erase boards, thumbs up), small groups (e.g., Numbered Heads Together, jigsaw, reciprocal teaching), and partner activities (e.g., Think-Pair-Share and peer-teaching). Though many of these techniques are not new, they allow teachers to provide interest and variety in their instruction, simultaneously engage all students, and conduct ongoing informal assessment of students' skills. (Contains 1 table.)