It has been proved that different media stimulate different parts of the brain. The more the number of areas of the brain stimulated, the better is the understanding of the topic, as well as the retention. Hence when a topic is being covered, ensure that you study the same topic from notebook, textbook, workbook, online resources, animated videos (if available), any other reference sources available, and finally teach someone what you learnt. Needless to say, it may not be possible for you to cover all of the above in a single session. Each time you study the concept, you could use a different medium.