When students learn skills to solve problems by teaching others, they often need to receive scaffolding to benefit from learning by teaching. To facilitate learning by teaching (aka tutor learning), two types of scaffolding have been commonly studied--the scaffolding on how to teach (to induce appropriate teaching activities) and the one on how to solve problems (to ensure correctness of solutions taught). The comparison between these two types of scaffolding and the adaptive control among them, however, has been left unresearched. The primary goal of the current study is to understand how to best control the scaffolding for learning by teaching. A technique for exhaustive differential pattern mining was used to correlate a behavioral pattern of learning by teaching with tutor learning. The results showed that only the scaffolding on how to teach facilitated tutor learning. Students who received the scaffolding on how to teach typically interleaved teaching and assessing their peers' competency more often than those who received the scaffolding on how to solve problems. The results imply an importance of implementing adaptive scaffolding on how to teach to better facilitate learning by teaching.