Firstly, I would suggest re-reading the books/plays/poems that you are required to know. If it is a closed book exam then it is important that you know these texts inside and out. Focus on important themes within the texts and try coming up with you own essay questions or create an essay plan based on these themes. I would advice writing a few essays in exam conditions as well to make sure you are comfortable with the timings.
Writing out your thoughts and ideas is a really good way to get to grips with the texts and to really understand them.