Read the topic list in the course syllabus. If there is no topic list, compile one by reading the headings of the classes, tests and homework assignments.
Choose questions from past tests and homework assignments that cover each topic. Quiz yourself on these questions and check your answers by using the answers provided on your test, along with any corrections.
Use of the results of your self quizzes to rank the topics from hardest to easiest. Review your class notes and textbook and consult with your study group or professor for help regarding the hard topics. Take advantage of your teacher's office hours.
Make a realistic study schedule and stick to it. Spread the work out evenly in the time you have left before the exam, allowing a bit of slack in case you fall behind. For example, if you need to review four chapters in two weeks, do one chapter every three days.
Find an environment that is conducive to studying. If you need complete silence, try a library. If you want to work with a study group, try a coffee shop or study lounge.
For each microbe or disease, try to incorporate as much information as possible into one sketch or mnemonic. This will help you to associate the information about each microbe or disease with the other the information about that microbe or disease.
When you think you have memorized all of the information, take a past year's exam, if available. If past years' exams are not available, retake your tests. Grade yourself and see which areas still need work.
Highlight any information that you tend to forget. Review that the night before the exam and again right before the exam.