Glad someone mentioned Albert Einstein. I remember there were several people last year that decided to get an "early start" and submitted the secondary before getting the official email invitation. BAM, automatic rejection. I agree that the best thing is to simply start pre-writing some secondaries based on last year's prompts. There are also a few common ones: if you're in a gap year, write about what you're doing. A lot of schools will ask you for a couple paragraphs about, "Why our school?" It's good to have these responses ready for interviews, anyway, so I'd recommend doing at least one paragraph for every school you apply to (if you have the free time). Some schools will ask for a couple paragraphs about where you see your future in medicine.