Although this sounds very straightforward, people don't often properly answer the question set and therefore don't get the band that they should even if the writing is very good.
First of all read the question very carefully in order to see exactly what it asks you. Very often there will be more than 1 part to the question; sometimes even 3 or 4 parts. When you produce your answer you must answer all the different parts of the question. How much you produce on each part depends on how important you think it is.
You have to write a formal academic English essay of the type that would be required for teachers or tertiary education courses. Formulate and develop an argument and show a personal response. Give your opinions and back them up with evidence and examples. Your answer should persuade, be consistent and develop logically towards a conclusion, which answers all parts of the question.
Another important basic is to write at least 250 words. Writing less does not answer the question, which tells you to write at least 250 words. If you write less than 250 words, the examiner marking your paper will give you a maximum of 5 for Arguments, Ideas and Evidence or even less. It is no problem to write more than the 250 words; there is no upward word limit on the essay. Time is your only constraint.
The question wants you to produce an essay. Therefore don't give a list of numbered notes (your paragraphs should not be numbered). Give the examiner a proper essay with an introduction, a main body with your ideas and evidence and a conclusion, all divided of course with the paragraphing techniques discussed above.