To investigate the strategies and approaches in teaching Computer Science (CS), we searched the literature reviews in CS education in the past ten years. The reviews show that learning-by-teaching with the use of technologies helps improve student learning. To further investigate the strategies applied to learning-by-teaching, three categories are identified: peer tutoring, game-based flipped classroom, and teachable agents. For each category, we further searched and investigated prior studies. The results reveal the effectiveness and challenges of each strategy and provide insights for future studies.