What do I have to do to get top marks in a long essay question?

Firstly, I would look at the exam board the student is using. For GCSE and A Level, marking criteria are usually a great starting point. However, for students they can often be too wordy and complex. Being able to look at the criteria and break it down into language the student can understand is vital. 

Therefore, I would assess the criteria, and explain to the student that for history two main things are important: coherence of the argument and knowledge of the topic. KNoweldge of the topic, if they are confused on something, is an aspect that can easily be worked upon. Coherence of the argument is far more difficult, and using a whiteboard diagram, I would show the student how to divide the topic into three coherent parts, each of which could be explored in detail in an exam question thus enabling a much easier answer.