One thing I took that was helpful was a small sheet of clear acetate with two thin lines drawn on it at 90 degree angles.
Helped follow the grids on those convoluted performance charts
This is good advice. Those performance charts can be a pain when your eyes are tired.
As for the test itself main advice is to just take your time. While it is timed (2.5 hours) you really shouldn't be under any serious time pressure. Everyone has their own approach, but this worked for me:
A few days before the test I went through my practice test booklet and highlighted any questions that tripped me up. Based on these questions I prepared a 'study sheet' of notes to focus on the items that I had issues with. The act of writing these down and then reviewing them a few times afterwards got my brain in shape on these items that had been tripping me up.
It was mostly the random multi-choice either you know it or you don't questions that this focused on--e.g., knowing that if you're busted for DUI it's the aviation security office and not the medical office that needs to be notified (this actually then came up on my actual exam).
I reviewed these notes a few times leading up to the exam, although didn't go nuts as cramming doesn't help.
During the exam itself:
1st pass through questions, skip and mark any questions that required calculations or interpolations, just focusing on answering the multi-choice questions. If I was not 100% sure of the answer I put what I thought was the answer and marked it for later review.
2nd pass go back and answer all the questions requiring calculations. Again if not 100% sure of the answer I keep it marked for review.
3rd pass focus on all the questions that I had marked for review for either not knowing the answer or not being 100% sure of my answer. Hopefully this isn't a huge number of questions at at this point you can relax a bit (knowing that even if you get every one of these wrong hopefully that still translates into a decent score).
Before submitting I just looked over everything once more quickly.
If you miss anything you'll be allowed to see the questions you missed, although they won't show you the correct answer.
Good luck!