The multiple choice questions cover a broad range of topics, therefore nothing is going to succeed more than a solid background in the subject. After that, there are some general test-taking skills that apply.
1- Read each question carefully. This is as much a reading test as it is a science exam. You will have an average of 54 seconds for each multiple choice question, one hundred questions in ninety minutes.
2- To ensure that you get the maximum number correct, it is important to at least see every question. Some of the questions at the end of the test might be very easy for you to answer. You just have to make sure you get to them in the time allotted. If you try to answer an early question that takes a long time to reason out, you may not even get to read the questions at the end of the exam. To guarantee the highest number of correct answers, start by reading the whole test and answering only the questions that you know the answer to immediately or with a minimum of thought. Go all the way to question number 100, even though you probably are skipping quite a few. Now you can be reasonably sure that all your answers are correct. Remember the 54 seconds per question. Time saved here can be used later to answer the questions that are more difficult.
3- Now go back and answer skipped questions that you can figure out with a little effort. Go through the whole test again doing this. Be very careful that your responses on the answer sheet match the number of the question you are answering. Again, probably all or most of these answers are correct.
4- Finally go through the test again, now concentrating on the questions that you are not totally sure of. There is a penalty for guessing. The scoring formula will subtract ¼ point for each incorrect answer while adding 1 point for each correct one. Random guessing to fill in your answer sheet will probably result in a lowering of your score. If you can eliminate two or more choices as being incorrect, it is to your advantage to take an informed guess. Statistically, if you guess at four questions and get three wrong and only one right, you will still add ¼ of a point to your score.