Recently, I was in the same position that you are now. I successfully completed the NREMT this month on my first attempt.
In my opinion, these are the things that helped me the most:
1.) Becoming comfortable with your EMT course materials. This may be a no brainer, but, regardless of question/exam format, you need to have a firm grasp of the concepts/material in order to apply it appropriately.
I would suspect that if you completed your course without any great difficulty, you're already at this point. But that is a personal determination.
2.) Limmer Creative's EMT Review Plus app. I believe there is a purchase price, but can't recall exactly what it was. This app provides study and review material along with 100 question practice exams. I found the practice exams to be most beneficial.
I can't verify this, but I was told that the creator of the app was/is a writer for the National Registry. Based on the question style between the practice exam and the NREMT Exam, I suspect this is true.
3.) Don't wait too long before taking the exam. This is where I made my big mistakes. I waited many months before finally taking the exam. Don't procrastinate. IMO, there isn't much to gain by waiting.
Those are the main points that come to my mind. I'm far from an expert, so keep in mind that this is just my opinion regarding what worked best for me.
Other than that, go in with confidence, and do your best. If you put in the work and honestly feel prepared, then you probably are. Take it one question at a time, and ask yourself what is best for you, your partner, and your patient. If you do that, you probably won't be wrong.
GOOD LUCK!