Close your eyes, breath deep, roll your neck, and let your tension go 2. Skip the questions you don't know, you can come back later 3. Review the material you do know in your head. Ask permission to get some water or sharpen your pencil. Maybe, but give yourself a positive edge.
Some people use a special pen only for test.
Some carry a lucky stapler, rabbits foot, or pacifier. Whatever it is, if it helps use it. Peppermint has been shown to boost alertness. It also has a jolt of sugar to feed your brain. Take a few peppermints into a test with you.