A mistake notebook is a habit that can be more effective than solving lots of questions: you write down what you did so you do not make the same mistake a second time.
What to write?
- The source and number of the question (book, practice exam, page).
- The type of mistake: knowledge gap, attention error or time.
- A one-sentence summary of the correct method.
- When you will look at it again.
A simple layout
Use a table or a notebook: date, subject, topic, type of mistake, correct method. Review it once a week; if the same topic keeps coming up, give it extra time.
For questions you get stuck on
Ask your teacher about a question you cannot solve, or look it up in a source with solutions. After reading the solution, write the method in your mistake notebook; the goal is to learn the reasoning, not the answer.