The mistake almost everyone makes
You open a past paper, read the question, then immediately read the memo. It all makes sense. You think: "Yeah, I know how to do that." You move on.
The problem: recognising a solution and producing one from scratch are completely different skills. Recognition feels exactly like knowledge right up until you're in the exam hall with a blank page and no memo — which is the only place it actually counts.
The method
Cover the memo completely — fold the page, use another sheet, whatever works. You should not be able to see a single mark of it.
Attempt the full question, on paper, exactly as you would in the exam. Write every step. Do not peek.
The moment you get stuck — not before — reveal only the next line of the memo. Not the whole solution, just the next step.
Write that step in your own working, then cover the memo again and continue from there under your own steam.
Why this works
This is called active recall, and it's one of the most well-evidenced study techniques that exists. Forcing your brain to retrieve a method rather than just recognise it is what actually builds the neural pathway you'll rely on in the exam.
It also tells you EXACTLY where your knowledge breaks down — the specific line you got stuck on — instead of the vague feeling of 'I sort of get this topic'.