There are known errors in thinking. Avoiding them can make you less likely to fall into the many reasoning errors that humans have been trapped in throughout history.
It might not make you 2% smarter on a test. It probably makes you 2% and more overall because you can examine your thinking for common classes of error, identity your mistakes and attempt to correct them.
Examine the known errors humans have made in their understanding of the world. Identify patterns in those errors, abstract those errors, apply the principles to your conclusions.
Here’s one: thinking there’s some source of truth written on commonly known that cannot be challenged. For centuries after the invention of the microscope germ theory was disregarded because a false theory of miasma predominated. Why? We got attached to pleasant sounding but made up story. We didn’t question it enough to allow the evidence before our eyes to update our thinking.
I leave exploration of other classes of errors in thinking as an exercise for the reader.
> Why? We got attached to pleasant sounding but made up story. We didn’t question it enough to allow the evidence before our eyes to update our thinking.
It bears mentioning that this isn't simply a matter of “everyone was wrong until a clever chap was first to question established wisdom and suddenly everyone was enlightened”.
It's more like “everyone enforces the established wisdom on everyone else and the clever chap is punished for being clever”.
I don't know if this applied to the germ theory, but it applied to plenty of theories the most famous of which being geocentrism. It's very likely that people before Copernicus questioned geocentrism, perhaps even thought of heliocentrism, but were either tortured or killed for it, or stayed silent from the get-go because they knew that would happen to them.
Lone clever chaps do not overturn established wisdom. It's a gradual process that requires a critical mass and a mountain of evidence.