From what I've heard
- clear address of question, no vague conceptual shit that says nothing
- specific context, again don't be vague
- at least 4 quotes with technique and analysis per body paragraph. 3 body paragraphs
do all that and I think you will not get lower than 16/20. anything else I have no idea.
I think you need a good introduction (~150 words) to WOW the marker because they may be lazy and will skim your actual essay.