Well, I would suggest reading any challenging piece of literature you find and just aim to improve your general writing skills. Practise! For the language, try doing papers and setting yourself random story assignments (Off the top of my head "Base a story around the the title "A knock on the door" ect.). Slightly less sure on the Literature (I'm in the process of doing it now =) ), but I would say learn your quotes + notes.
Advice based on an A* in early entry Language and the fact that i'm currently doing the English Lit course.