[In listening to teachings one] of the defects is to listen in a way that is like a container with holes. This means that even though we are listening to the teachings, we do not retain their contents. In this case, we lack mindfulness and memory. Practice of Dharma means that we should be able to benefit from what we have heard. It is not a pastime, like listening to a story. The teachings give us guidance on how to live meaningful lives and how to develop proper attitudes. So in order to benefit from the teachings, we must retain them with mindfulness.
In all kinds of learning processes, listening, reading, etc., we must pay full attention and should endeavor to remember their contents. When our interest is halfhearted, we only remember half the points, and we retain them for only a short time. We should reflect and think about whatever we have heard, over and over again. In this way, the knowledge will stay in our mind for a long time. Another technique for remembering instructions is debate as it is practiced in the traditional debating schools. (p.22)
from Stages of Meditation by the Dalai Lama, root text by Kamalashila, translated by Geshe Lobsang Jordhen, Losang Choephel Ganchenpa, and Jeremy Russell, published by Snow Lion Publications