At an early stage in your preparation for a supervision essay you should decide (if you have been given a choice) which essay title you are going to write on. A small amount of reading may be necessary to decide this but if you have been to the lectures you will probably have enough knowledge of the topic to know which aspect you want to study for your essay.
Once you know which title you are going to write on, spend some time really thinking about the title; think about each word, and what it means; ask yourself which words in the title are the most important, and which are ambiguous or in need of definition; think about what evidence would be relevant to the question; think about the different possible approaches to the essay, and which one you might favour. You could also break the title down into two or three sub-questions, and then break those down further until you have several basic questions, the answers to which, together, will form a coherent answer to the question. The following is an example of how this might work:
It is essential that you do this sort of analysis before you start doing your reading. This way you will go to the books with a clear set of questions in mind, knowing what material is less relevant and can be skimmed over, and which pages of the books you are reading are the most pertinent and need closer scrutiny. As a general rule, you should not open a book not knowing what you are looking for. If you don't know what you are looking for, you have an extremely small chance of finding it.