For all year 12's english SACs I memorized my responses.

Then when I got to the exam period I realised this was VERY BAD exam prep. I had not done many practice essays and the text response question in the exam was one I had completely not touched on before.
Like others have said, if you're not very talented in English, memorizing ideas that fit into a range of questions would be adequate. (this is only for text response)
For lang analysis, do what TrueTears did.

(which is how I survived it too)
Context....well, I do not know how to give advice for this one as I was swinging between expository and creative all year. In the exam I just came up with something completely random and spontaneous (something like 'chasing pregnant sheep' if I remember correctly....since the Imaginative Landscape prompt was stupid)
If you're confident in english, write your essays from scratch both in SACs (good exam prep) and in the exam. If not, then write lots of essays and memorize the ideas which you think are better and more likely to come up in the questions.