I have given the subject of how to think clearly an incredible amount of thought. I would first suggest reading as little as possible. Less reading, more thinking. Reading entire books is especially hazardous and should be done with great care not to pick up the bad habits of the author subconsciously: “It’s not what you know, it’s what you know that just ain’t so.” (And also the reasoning habits you think are legitimate because famous people use them, but they aren’t.)
Here are my recommendations for how to think clearly.