No matter how left-field the questions/SIMs are, keep with it, and answer them to the best of your ability. I swear I had 2-3 SIMs I knew NOTHING about, but I had time to research, and walked away with an 85.
Try to hang on to confidence no matter how hard the test beats you down.
Expect to feel as if you failed miserably regardless of how you did, so don't beat yourself up. You WILL feel terrible walking out; I did for at least 3/4 tests and passed them all.
Get there early to avoid any additional stress. Drink a smoothie beforehand (preferably with lots of kale; it will make you feel awake and sharp, but not jittery and nervous like caffeine).
Budget your time per testlet and per SIM; Gleim recommends you write down your budgeted time for each section as soon as you sit down, and fill in your actual time next to it. If you can leave more time for the SIMs, you will likely need it. Bring your own ear plugs. Don't forget your NTS and ID. See if you can notice if testlets #2 and #3 are harder than #1. (That said, FAR was the one test where I did not feel like they were getting harder.) If they get harder, it is usually a good sign. Remember that questions are weighted differently and there are many pretest questions, so several wrong questions are not necessarily a bad sign.
Good luck!