Arrive on time. Sit where the light is good and where there is a minimum of distractions from other students during the test and as they are leaving.
Most teachers give fair tests.
They usually are not attempting to trick you but rather want to know how thoroughly you have mastered the information. Take a deep breath, hold it and let it out slowly. Repeat this several times to help eliminate tension which can block thinking and memory for information. Read the directions and follow them. Make sure you understand what is expected of you.