Its not a bad idea to prepare part of your essay/short answers. What I did was memorise the body of my essay, then on the day I'd add in my introduction and conclusion as well as my opening/linking sentence for each of my paragraphs. I did this so I could mould my answer to fit the question better. With SOR the syllabus is very narrow, so the questions, whilst sounding different each year, practically ask you to do the same things.