Great advice, previous posters.
I think the psychological factor is as big as the technical aspect of studying. For every one of my tests (and I passed all 4 on the first try, thank you Yaeger) there was a point (or many points!) where I hit a wall and panicked — I wasn't getting anything, I had no decent recall of stuff from previous chapters, it was way too much material to grasp, let alone master, I was sitting alone at midnight, exhausted, I just bombed 6 MCQs on a subject I thought I knew. You need to power through your personal walls whatever they are and and whenever they hit.
Test Day minutia: There is some helpful stuff you can do in the minutes after you start and before your initial screen times out — write down a few mnemonics or formulas, maybe write down 1-30 or 1-24 for each testlet on the side of your scratch paper sheets to cross through or circle if you don't want to click questions for review on the screen. Take 3 deep breaths. Write “Go Kelly” on the top of your scratch paper. All of this helps give you a sense of CONTROL.
Target time for the first testlet: 30 minutes or less. You CAN do most of the SIMs if you leave yourself enough time to figure out or research what they are asking.
If you balk at paying $30 for the Prometric dry run, just show up at the center after you schedule but before you test. They won't let you try the computer and they may not like it that you're there (be prepared to show ID), but you can see the layout, where the bathroom is, ask about parking. If your Prometric staff are mean and nasty on test day, don't let it throw you off. You can complain about them later and schedule your next test at another center.
5. Ask any athlete or performer — rituals help calm you down and focus. Eat your special breakfast, wear your lucky underwear, chew peppermint gum to aid recall, whatever.
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