A Quick Guide to the Most Effective Study Method, According to Research
Effective students are ones that save time and retain what they learn.
Exams require you to retrieve and interpret information that you have stored in your mind throughout the semester. However, because of the forgetting curve (posed by Hermann Ebbinghaus), we tend to lose this information unless we retrieve it frequently. An effective study method must, therefore, allow us to store and recover as much information as possible.
Fortunately, there is one such method — that also saves time.
I used to spend hours every day taking notes and re-reading them, only to forget most of it anyway. Now, I remember all the important information I read, whilst spending a mere 20% of my previous time studying. It is this study method that has been deemed the most effective one by researchers.
Active Recall combined with Spaced Repetition.

I learned all of this information from Ali Abdaal, whose in-depth Skillshare class I took to learn Active Recall and Spaced Repetition. This article is a quick guide to that method, that summarizes the most important things I learned from him.
Step 1: Read one unit of the material
Focus your attention on one part of the material — for instance, an individual paragraph or presentation slide. Make sure that you understand the material before you proceed.
Step 2: Repeat the information you have read
In your own words, repeat the central aspects of the information you have read in that one chunk, preferably in simple terms. Do this without looking at the source. This is how you best commit the information to memory.
Step 3: Write down questions and page numbers
Convert the information into one or two open-ended questions — ideally ones that start with How, Why, or Which. Do this only if the content is relevant to the exam or your own personal learning. After all, only some of the information you read is salient. Write your questions down, alongside the source page number on the bottom of the page.
(Because note-taking merely summarizes or copies the content already present in the textbook, it is a passive time-waster. By writing down questions instead, you engage with the material in a more active way. That way, if you need to “check your notes” later on, you can just refer to the original source found by using the page numbers.)
Step 4: Do an initial round of Active Recall
At the end of your session, answer all the questions you have written down in any order you want. If your memory fails you at some point, use the appropriate page number to find the answer in the original source. Decide upon the next date for you to do these questions next, depending on how good your memory was.
This is how a page of Active Recall questions can look like:

Step 5: Make a Spaced Repetition table
Dedicate a page to your to-be-made Spaced Repetition table. Write down each main topic within a specific course vertically down that page. (To me, a textbook chapter constitutes a “main topic”.) Horizontally next to each one, write down the date of your future revision of that topic’s questions.
Step 6: Revise when needed
Do Active Recall throughout the semester leading up to the exam. Each time you finish a round of this (like in Step 4), you must write down the next date of Active Recall in your Spaced Repetition table. When and how often you revise each topic depends on your how well you did on the last round of questioning.
Use color-coding on the dates to mark how well you did each time:
— Green: Great performance. The next session can be in more than a month.
— Yellow: Mediocre performance. The next session can be in 2–4 months.
— Red: Lackluster performance. The next session must be soon.
This is how a Spaced Repetition table can look like:

In the end, you will save a lot of precious time. Instead of reading and rereading heavy loads of text, or spendings weeks taking notes and hoping they stick to your brain, you can confidently and casually accumulate your knowledge by merely writing down some questions and repeating those questions at certain intervals.
Believe me, it makes a difference.
Summary
The most valuable and time-saving study method to date is Active Recall and Spaced Repetition:
STEP 1: Read the material in chunks
STEP 2: Repeat what you have read
STEP 3: Write down questions and page numbers
STEP 4: Do a round of Active Recall on all the questions
STEP 5: Write down the next date in a Spaced Repetition table
STEP 6: Revise when needed, throughout the semester