Create a schedule based on your exam timetable. Your plan should include plenty of time for studying, regular breaks and solid sleep time. Even if you don't stick to the plan, it helps you organize your approach.
Think positive. An exam crucial to your final grade increases stress levels. Adopt an "I can do this" attitude instead of thinking about what happens if you don't do well.
Start early. You may not have time before classes end, but as soon as they do, get to it.
Stay away from anxious people. Hanging around with constant worriers increases your stress. Hang out with people who relax you, and make your own calm cocoon for work periods.
Study in a logical sequence but with variety. The heavy science course in which you've struggled all semester may need most of your attention, but a lighter subject should follow that session.
Tell your parents to step back, if necessary. Some parents can be supportive and helpful while others can contribute to stress. Tell them you need to focus in order to survive your exams and that you plan to check in by email.