There are a number of different exam types. Preparation for these and techniques adopted within exams differs.
Past papers are helpful when preparing for an essay based exam.
These will not only give you an idea of the range of questions you may be asked but also the wording of questions. Use these papers to practise for your exam. Analyse sample questions, write an introduction and jot down the main points you would use in order to support your response to the question. This form of preparation allows you not only to test your recall of the content of the different topics you have covered over the semester but more importantly to apply that knowledge to the question asked. Remember that essay exams aim to test understanding of the course material not simply recall, although recall is certainly a part of your preparation.