Last minute ACT prep

What are some ways to calm down during the test? I know that on real tests, I significantly do worse than on practice tests due to my mind being completely blank for the first few minutes.
In addition, what would you say is a good pacing time for the essay section? (As in, how long should I spend on what?)

The best strategy is to literally do so many practice tests that it becomes second nature to you. I did like 15-18 tests in preparation and got a 34.