Some simple (but really important) rules:
Read the rubric:
how many questions do you have to answer?
does the paper have 1 section or several?
do you have to answer at least 1 question per section?
are there restrictions on which writers / texts you can write on?
Read the question:
Everyone knows this is vital but people often forget when under pressure.
Underline key words in the question. This will help you to stay relevant and to answer every bit of the question.
Keep glancing at the question every so often to check that you’re actually answering it!
Don’t waste time writing about anything which doesn’t answer the question: don’t tell the examiner when a writer was born, the history of the period etc unless it’s relevant. If you’re asked to discuss politics then of course a few points on political history would be great but only if they are relevant to the question.
If in doubt, imagine you’re a lawyer having to defend your case in court. ‘I feel’ won’t cut it 🙂
You need to establish a clear argument and provide a series of relevant points to make your argument convincing.
See my notes on writing essays for more info on how to construct relevant convincing arguments.