Sleep first. The nights before count, not just the night before. A rested brain beats a crammed one every time.
Keep the morning boring. Eat what you normally eat. Don't change your routine on the one day it matters.
Arrive early. Give yourself a buffer so traffic or parking doesn't spike your nerves before you've started.
Read the instructions like they're new. Careless mistakes almost always trace back to a skipped line.
If a question stalls you, move on. Rule out the obvious wrong answers, make your best guess, and come back to it. Don't let one hard question rattle the next ten.
And the day before: be done by early afternoon. One more pass through the notes won't help as much as a full night's sleep will.