When you're learning something you don't know what you don't know, which is why teaching the thing is often said to be a great way to learn more about it. You n

When you're learning something you don't know what you don't know, which is why teaching the thing is often said to be a great way to learn more about it. You need to understand it well enough to be able to simplify it, and you get asked questions by the person you're teaching that will test your knowledge. Find Q&A sites that talk about the think you're trying to become expert in and try to answer as many questions as you can. You don't have to actually answer the questions -- those sites are often hellscapes.