How do you make your notes useful?

I am curious, if you take lots of notes on what you learn, how do you structure them so the information is easily accessible and useful for review?

I came across the slipbox method from the book How to Take Smart Notes. I have been trying to apply this with the Obsidian app. But when I want to go back and look over the notes, there just does not seem like a surefire way to review them.