I would begin by reading and re-reading your texts at least two or three times before your exam, more if your revision timetable allows. Make notes and highlight key quotations and moments while doing this, as whether or not your exam is open book, you should have a good working knowledge of the text in order to work efficiently in the exam. Identify key themes, ideas, motifs, symbols and significant character moments and take the time to find interesting and original quotations to support these, as this will suggest a personal engagement with the texts. If the exam will be comparative, think about how the two texts respond to the same ideas - for example, how Lord of the Flies and Animal Farm demonstrate different or similar ideas about power.Try and take the time to read around the text contextually - find out some more about the author and the time and place in which the text was written. It is really important that you show an awareness of how the context shapes the text itself, but be careful with how you use this in an exam - your exam response should be analytical, not descriptive. As with other subjects, it can be good to have group revision sessions, to check you are reading the text in appropriate ways to allow you to develop your own ideas fully, but online resources can also be useful for this.