From John Hattie, Visible Learning.

Visible teaching and learning occurs when learning is the explicit goal, when  it is appropriately challenging, when the teacher and the student both (in their various ways) seek to ascertain whether and to what degree the challenging goal is attained, when there is deliberate practice aimed at attaining mastery of the goal, when there is feedback given and sought, and when there are active, passionate and engaging people (teacher, student, peers and so on) participating in the act of learning.

As you can see, I enjoyed reading it.