I assign my students homework to be completed before our next session. The homework is usually specific and focuses on filling any gaps in their knowledge I discover during the previous session(s). I verify the gap is gone by thorough questioning and testing. By doing this, I help my students develop confidence, competence, and mastery of the subject so they may avoid a "train wreck" later on when they take a test in school or use the material at work. Filling in knowledge gaps as they are discovered is an effective way to achieve these goals, but this is not the secret to learning mathematics. There are some teaching techniques that work better for some people than others but, in my opinion, mathematics is best learned through regular and frequent practice and experience. Math skills are perishable and improve through cumulative study; i.e., build math strength through effective mental workouts. If there is a "secret" to learning math, that's it!