You need to have a clear idea about the syllabus and everything that is involved in the course of learning. Your instructor will also be tracking your progress on regular intervals; you must talk to your instructor about the same to understand where you are standing and what you need to work on. They will provide you with a training outline and also a syllabus covering everything that you need to know.
Going through previous FAA written test papers and model papers is another way of preparing for the final written exam as it allows you to have a clear idea about what to expect in the examination. All the best.