“The person who says he knows what he thinks but cannot express it usually does not know what he thinks.”
― Mortimer J. Adler, How to Read a Book

Step 1: Teach it to a child
Take out a blank sheet of paper and write the subject you want to learn at the top. Write out what you know about the subject as if you were teaching it to a child. Not your smart adult friend but rather an 8-year-old who has just enough vocabulary and attention span to understand basic concepts and relationships.

When you write out an idea from start to finish in simple language that a child can understand (tip: use only the most common words), you force yourself to understand the concept at a deeper level and simplify relationships and connections between ideas. If you struggle, you have a clear understanding of where you have some gaps. That tension is good –it heralds an opportunity to learn.

Competence is knowing the limit of your abilities, and you’ve just identified one!

This is where the learning starts. Now you know where you got stuck, go back to the source material and re-learn it until you can explain it in basic terms.

Identifying the boundaries of your understanding also limits the mistakes you’re liable to make and increases your chance of success when applying knowledge.

Step 3: Organize and Simplify
Now you have a set of hand-crafted notes. Review them to make sure you didn’t mistakenly borrow any of the jargon from the source material. Organize them into a simple story that flows.

Read them out loud. If the explanation isn’t simple or sounds confusing that’s a good indication that your understanding in that area still needs some work.

Step 4 (optional): Transmit
If you really want to be sure of your understanding, run it past someone (ideally who knows little of the subject –or find that 8-year-old!). The ultimate test of your knowledge is your capacity to convey it to another.