Read the question carefully several times, noting key words, different possible emphases and thinking all the time about exactly what the question is getting at.
The Bloody Chamber: AS & A2
Identify five or six key points that answer the question; plan an introduction, a development of an argument and a conclusion.
Stick to your plan and be succinct and to the point in your writing: keep to the appropriate time for each answer.
Always plan to give yourself a few minutes at the end to read through your answer and pick up on any glaring omissions or careless errors.
Be as detached as possible; keeping calm will help you time yourself, stick to plans, ensure you answer the question and find the right quotations.