One of the things that I wish I’d known during my school years is the technique of spaced repetition. The TL;DR is that it’s a method for learning and remembering material that’s much more efficient and reliable than other common methods, especially cramming. The basic idea is that you revisit material based on ever increasing intervals determined by how well you remember it.
As Ali Abdaal says, there are rigorous studies that show the effectiveness of the method. Adaal has a whole series of videos that explore spaced repetition and other strategies for effective learning. Those videos are the easiest way I know to explore the method. He recommends using active recall in conjunction with spaced repetition for maximum benefit.
There are, of course, numerous applications—including Emacs packages—that implement the space repetition technique. If you’re still a student or otherwise need to learn a collection of facts, spaced repetition is almost certainly your best bet.
If you want a quick and easy introduction to spaced repetition, Nicky Case has a cartoon based explanaton of the method that’s easy and enjoyable to read. Case’s post is from 2018 but is still relevant today. Take a look at it and see how easy learning things can be.