One way to learn is to ask yourself questions, and then to answer them — which usually leads to more questions. This question/answser style is sometimes called the method of inquiry and is based on the ideas of Socrates.
But what questions should you ask?
Here is a list of questions that can help you get started. It is not an exhaustive list. You should be able to come up with more questions that just these; but these will get you started.
The questions are arranged into four levels. You should start with level 1 questions and work your way to level 4 questions.
Given any concept, idea, or thing (e.g. free body diagrams, or staplers, or hospitals), just substitute it for XX in the questions.