A few things more.
You do all this brainstorming as a rough work, on the very last few pages of the answer book, even you can do this on 4, 5 pages. during this process, try to bring out all relevant material onto the page. Analyse every point whether it relates to the topic or goes in a bit digression. Also try to bring out any relevant quote if you can. However it does'nt matter if can't manage any quote in your essay; your idea on the topic is given the supreme value. Now if you think that you have produced the best possible outline, try to make it neat in 5 minutes. If making outline takes you even one and a half hour, you can still write your essay in the remaining half period. The examiner is more interested in quality work. So dont worry about length. Most of candidates write about 15-page essay and succeed given the measure of relevance of your idea.

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Success usually comes to those who are too busy to be looking for it.