here's a tip that our English teacher gave us for studying:
randomly pick a year from your past papers book and then read the questions. pick a question and draw a wee spider diagram for it, basically a plan for the essay.
A short story I'm doing is "A rat and some rennovations" and there's a question that says look at a novel or short story that uses humour to tell the story...
In the middle of the page I would write humour, then I'd write the different types of humour, and then I'd write the most important humourous incidents from the story with quotes... and hey presto, I've studied!

and then I just pray that an easy question like that comes up, and not one about symbolism or the narration from the story. If that happenes, I will cry.
This will show you what you need to study more and what you already know.