The safest way to enter into an A-Level music exam is less about 'knowing' your set works off-by-heart but instead about being aware of the 'key points' and overall structure of your pieces and their contexts. Frequent listening and score analysis will help you to familiarise yourself with the composer, genre and style of the works. This continued exploration of the work will also help with your 'aural' exam since listening to a given piece allows your ear to grow accustomed to searching for specific features, alongside improving your key and instrument recognition. When approaching an exam condense your notes into the "need to knows" such as specific contextual details, melodic themes and tonality, and allow a well rounded knowledge of the mood, specific key changes and relevant 'filler' material. If possible have twelve relevant points for each essay you may need to write and commit them to memory. Ensure your spelling is totally correct - there is nothing more frustrating than reading the name of a composer which is horrendously misspelt.