Definitely what True Tears said. I did this for the film Look Both Ways, as all the themes are connected etc, so I had paragraphs on 3 main characters which I was able to alter according to the prompt, but the majority of the para was the same as what I had been writing in all my practices.
I struggled at English in year 11 (failed my first SAC) and this year got up to the top 5 or so in our cohort of around 80, and I owe it all to constant practice of essay writing. For each SAC, I read the book/watched the film a number of times, and then got a hold of as many prompts and questions I could and wrote essays on all of them. I also got my teacher to correct them so I could rectify the problems in the next essays, but this is definitely the best way to go, IMO. Same with language analysis, I did as many as I could.
In relation to the exam, I did as many practice exams as I could, to time. This often required gathering a prompt for a text response, context, and an article and just doing them in 3 hours. I have no doubt that without the work I did, I'd be looking at a 25 in English this year, but instead I'm hoping for a high 30; this improvement is undoubtedly due to the practice I did.
And like xoxogossipgirl said, when you're writing your practice essays, you'll be sure to come up with quotes/sentences/terms/words that are just gold, so try and memorise these and intertwine them into your essays. I also didn't need to memorise quotes, as I had watched/read the texts so many times I recalled many quotes.