Taking notes while reading can supercharge your retention of information (if you do it right).
However, when we’re taught how to read read, we’re not allowed to write in books. So we never really learn a system for taking notes that we can use as adults.
The first step to taking notes is to figure out why you are taking notes. If you’re studying for an exam your notes are going to look different than if you’re reading for entertainment. The way you take notes depends on the reason you’re taking notes.
Like almost everything in life, there is no magical answer that fits everyone. You’ll have to do a bit of trial and error and take what works for you.
Step One - The first thing to do when you pick up a book is read the preface, the table of contents, and the inside jacket. This doesn’t take long and often saves you time, as a lot of books do not make it past this filter. Maybe it doesn’t contain the information you're trying to gain. If it seems crappy, flip to a few random pages to verify.
This filter is a form of systematic skimming. This isn’t our term, Mortimer Adler, a guy who literally wrote the book on reading, came up with it. Adler says there are four levels of reading.
While reading, take notes. Circle words you need to look up. Star points that you think are critical to the argument. Underline anything that strikes you as interesting. Comment like a madman in the margins. Try to tease out assumptions, etc.
Essentially, engage in a conversation with the author. Maybe your questions will be answered on the next page or in the next chapter. Maybe you'll need to find another book to answer them. Who knows. But write them down.
At the end of each chapter, write a few bullet points that summarize what you’ve just read. When you're done, write a brief summary of the entire book and then do something few other people do. I let the book age.
Put the book on your desk and don’t touch it for anywhere from a few days to a week. This is very important.
Step two - When you pick the book up again, re-read every scribble, underline, and comment you've made (assuming you can still read your own writing).
You're not the same person you were the first time you read the book, two things have changed: (1) you’ve read the entire book and (2) you’ve had a chance to sleep on what may have seemed earth-shattering at the time but now just seems meh.
If something still strikes your interest, write a note in the first few pages of the book, in your own words, on the topic. Often this is a summary but increasingly it’s ways to apply the knowledge. Index this to the page number in the book.
Sometimes, and this depends on the book, you can create a sort of mental summary of the book’s main arguments and gaps and sometimes you can cross-link points with other books.
Step 3 (optional but highly effective) - Wait a few days. Then go through the book and copy out excerpts by hand and put them into your repository or commonplace book. Use these notes to connect and synthesize ideas as you read.
To aid recall, connect the ideas to something you already have in your mind. Is it a continuation of the idea? Does it replace an idea? Is it the same idea in a different discipline?
Add these connections to your notes and percolate them in your mind.