There will always be insights you have gained from previous questions that you can use for your answers. You don't need to start from scratch every time you see a new question.
The trick is to recognise the familiar parts of a question and to exploit that familiarity. You can translate elements of your previous answers to new answers once you have identified which aspects of the questions are the same and which are different. There is only a finite number of forms that a question can take, and a limited syllabus on which questions can be based. The recycling of material between exams is inevitable.
After doing a few past papers for a particular subject, you will probably have seen every type of question that can appear in an exam. Patterns will emerge, and you will develop a feel for what to expect. As with many aspects of exam-taking, this will happen naturally as you work through more and more practice questions. Equipping yourself with this exam sense means fewer surprises, greater confidence in your answers, and less time wasted trying to interpret questions.
It is not uncommon to see questions of the same format appear year after year just with some small changes. These changes could be numbers for a mathematics exam, certain passages of a text in a literature exam, or even the phrasing of the question itself.
This means that the format of a question is a clue to the answer. A question that initially seems difficult can become very straightforward once you realise that you can answer it by following the same steps as for a similar question you have seen before. This is true for any type of question and any subject.
Consider the following question as a basic example:
How does the author create a sense of tension in this passage?
It could be asked about any passage from any book. The book and passage may differ between instances of this question, but if you have answered this question before for a particular book and passage, there will be elements of your answer that you can translate to your answer for a different book and passage. Or perhaps the same book but a different passage. If “tension” were replaced with “sadness”, the content of your answer would probably change but you could very easily preserve its structure.
Since I have a science degree, I didn't answer very many essay questions at university. The following advice is from a PhD student at Cambridge who specialises in essays. He also received the highest score in his year for his Master’s degree (this is a different person to my LSE friend).
We've already discussed the fact that essay questions often share a similar structure. However, it is crucial that you point out the differences. Otherwise you will do what most students do. They read a question on X as "tell me everything you know about X". This is a mistake.
There will always be a flavour to the question that makes it different to other questions. This is the Twist.
Recognising the Twist dramatically increases your chances of achieving top-band answers. Mention it very clearly in your introduction and you will immediately demonstrate that you have identified the part that most other students have missed. Once you have done this, you can continue with your essay using the versatile unit strategy from Part 2.