I found this difficult at first, especially coming from GCSE where the book was there for you to constantly refer to. However, I found that the best way for me to remember quotations, was for me to relate them to relevant themes and ideas. For example in the Portrait of Dorain Gray I would list a handful of quotations under the heading death. Alongside these quotations, I would then write my anlysis in relation to the theme or idea they were under. This way I went into the exam with a lot of analysis already noted and it made it easier for me to keep track of quotations, so I was sure that I had enough and I wasn't repeating points.