I have my own highlighting system. It’s a color-coded system in which I flag books by primary colors with post-it notes. There’s blue, red, green, yellow, and orange. Each of those colors I’ll use to flag certain sections in a book. I call it the BAGEL method.
It starts B which B stands for Big Idea. I use the blue flag for anything that’s like a big idea, things that summarize the chapter or the book.
Then there’s the red flag, which I actually think is the most important. A stands for Antagonism. That’s something that is causing a cognitive dissonance or confusion, or some sort of friction in your mind. So if you read something and you feel like you don’t agree, you use the red flag. Keeping track of everything that confuses you can change your worldview, when you thought the world would work one way and it actually works in another way.
The G, which uses the yellow flag, is for General Idea. I use it to flag a main idea within a chapter.
The E is for External Reference, and that’s going to be the orange flag. You can flag any sort of research that’s referred to, so you can look into it later.
Finally, the L is for Lists, when the author goes through several supporting points. The green flag actually came about because I kept on running out of the yellow flags, so I needed a way to flag parts where a lot of points were coming up.