Know exactly what the question and the specification wants from you, devour the books you're required to study, look at critical essays related to the books and the concepts, and keep practicing. Also, refer to the exemplary essays provided by AQA to get an idea of the different standards of work, and try to emulate your writing style to fit your desired standard.
Remember, practice is key. Do all the past papers as many times as you can and keep improving them each time. GET FEEDBACK.