Many community colleges offer critical-thinking courses, so that could be an option.
There are many books on critical thinking. One with exercises that I can recommend is Kirby’s and Goodpastor’s “Thinking” (which could be used as a course book for a critical-thinking skills course). You might also check out books by Rolf Dobelli, Peter Bevelin, and Donella Matthews.
Farnam Street (fs.blog) and sites like it champion the idea of using mental models to think. Farnam Street has lots of good, free materials that you can start with and try to start using in your daily life. The site also recently put out a series of books called “The Great Mental Models”.
But mental models can be found everywhere. For example, I frequently use Nassim N. Taleb’s mental models of “robustness,” “antifragility,” and “skin in the game.” Likewise, I use the concept of expected value when making decisions.
Another good book with easily implemented mental models is “Judgment and Managerial Decision-Making”.
There are tons and tons of books in this space, and you will find many recommendations of good ones here on HN. Just search for book recommendations (an evergreen topic here) and you’re bound to find some.
But if I understand your post correctly, you seem to be trying to learn how to articulate your thoughts more. You could start with the simple but powerful practice of asking yourself, what is this person/book/podcast/etc. saying? Is it true / do I agree with it? Why or why not? And what of it / why does it matter? (These questions are similar to those suggested in Mortimer Adler’s “How to Read a Book”, which is another title I commend to you.)
Take notes when listening and reading, and try answering these questions out loud or in writing after hearing or reading something. It’s a practice, and engaging with the habit intentionally and repeatedly over time will help you to improve your skills.
In this regard, I can suggest the following practice too. Copy the text of a piece of writing and dump it into a plain text file. Open it with an editor like Sublime Text (which I like because it, and other text and code editors, makes it easy to move lines of text around). Then, put every sentence on its own line. (If you’re handy with computers, you can do this quickly with regex, or even find-and-replace.) Next, try rewriting each sentence to simplify it and to restate it in your own words. Then rearrange the lines to restructure the argument in the way that makes the most logical sense. Finally, you can analyze it and write out your reactions to it, or your counter-arguments.
By using this process, you’ll probably discover that many people have little idea of what they’re talking about, and that they articulate their thoughts poorly. You’ll also discover that much of what they say is opinion, and that they use various tricks to hide or warp ideas. On this note, studying Western rhetorical tradition may prove very helpful in your quest to learn how to think better (plenty of theoretical and how-to books there, going back to the Ancients!).
At any rate, you’re in good company here: HN is full of people who think about thinking and strive to think better themselves. I’m sure you’ll find many useful posts and comments from past discussions, as I have. It’s a lifelong journey that has no clear endpoint. That’s the challenge and the beauty of it!
Good luck, and let me know if you think I can be of assistance.
PS: Other writers and thinkers to definitely check out on these topics: Charlie Munger; Richard Feynman; Daniel Dennett (“Intuition Pumps and Other Tools for Thinking”).