wide variety of reading. get a history of CF and work through it so you know what CF is based on, and how it has changed...
prolly a bit early to go looking for RM, but if you see some you find appropriate, keep it.
look at how CF youve read is distinctive in its era (it is, trust me), and think about what makes it distinctive - conventions, social values, contexts etc etc.
its probably a good idea to consistently write essays throughout the year, just to get them down pat. Really wish i had...
Jellymonsta's advice is good...essays galore! Also be smart in your essay writing - pick different types of questions to respond to so you're not monotonously regurgitating the same thing again and again.
Essay questions generally fall into one or combinations of three basic types:
1) Conventions questions (where they ask for them, then ask you how they have been subverted, and to what effect)
2) Values questions (where they ask you what the composer is trying to show through their subversion of conventions, and other anecdotes they choose to incorporate into their work)
3) Contextual/Interpretations Questions (which ask you how these values themselves have changed over time, in which you can incorporate critical interpretations, etc.)
As for the creative questions - write as much crime fiction as you can yourself, be it crappy or not. And complement your composition with wide reading (as in much more than the set texts) so that you can learn to imitate certain styles, as well as note down conventions.
What really made 3unit good for me this year was the big group presentation we did - doing personal research and choosing to extend yourself and learn about things that you want to learn is surely the most enjoyable and best way to learn.