In two simple words, “Teach it!” Reading something is nice, writing down notes to help you remember key points is better, but if you really want to commit what you’ve learned to memory, share it with someone else.
Taking notes reinforces what you’ve learned, especially if you think further about the subject or idea while doing so. But unless you decide to research the subject in more depth, you’ll only have limited knowledge.
That’s why if you really want to understand a subject, you need to teach it to at least one other person. Consider the following points: