The most energy-hungry part of the human body is the brain. Our large brains are what set us apart from other animals and have made us one of the dominant species on this planet. To me, it makes sense then that when we do that hard work of thinking we should try to get the best return on the energy we spend. The best way to do that is to write.
When I write, I challenge my understanding of my ideas. I am forced to distil them into clear sentences rather than loose thoughts and feelings. I can ask questions about my writing and when I don't get answers I instead get topics for further research. With my thoughts on paper (or a screen), I find it much easier to have discussions with myself about those ideas. It feels very similar to the idea of rubber duck debugging.
How I take notes
After reading Building a Second Brain by Tiago Forte I've started to organise my notes by actionability. I use what he calls the PARA method. I'll not be covering what that is in this article, but the most important part is that I have a list of projects/problems that I am actively working on. When I'm consuming content (articles, videos etc) I'm mindful of this list and if the content might be relevant to any of my projects. If it is, I'll make a new note linking to the content and I'll write a few words on my interpretation of it and why it is relevant to my work.
Later, when I'm working on a project, I have a bunch of notes linking to relevant content along with what I was thinking when I first watched/read it. From there I'll refine my notes, add to them, or delete them if I no longer think they are relevant.
I use Obsidian for writing and note-taking, but it doesn't matter what app you use. What matters is getting your ideas out of your head and challenging them. Find out what you're missing or if you have any contradictory thoughts or ideas.
If you'd like to see how effective writing is for leveling up your thinking then try the following:
Using whatever note-taking app you like, create a new note and write down a list of what you believe are your core values. Pick any one of those values and explore it. Write about why you hold that belief and what experiences led you to it. Do you have any other beliefs that are counter to it? When was the last time you modified your behaviour because of that belief and was it worth it? Next, try this again, but instead of writing about it, do it in your head. With the written example I'm certain you'll have gone deeper and have a better understanding of that part of your identity.
Conclusion
Writing is a tool for thinking. It forces you to slow down and make sense of your thoughts. It can be used for introspection and for exploring the world around you. Next time you come across something that piques your curiosity, try writing about it.