Making 100's on any test is hard to do. I managed to make a few of them so far in nursing school, but honestly--I got lucky. I studied hard, and understood the structure of the question, but sometimes despite studying hardcore, some instructors pull questions out of their @ss.
The easy answer of how to make 100's on test is to roll the dice and hope for a seven. (little casino reference there, hehe).
The times where I made mid to high 90's on nursing tests were when I understood the information backward and forward. For example: it's not enough to know where a certain bone is located, you have to know it's function and WHY it's located where it is. In nursing school, that is the kind of effort you're going to have to make in order to make decent grades. Just memorizing doesn't work. I can memorize really well, but if I don't know why I know the information, I'm doomed.
An example of how a nursing question might be presented is something akin to this:
Your patient has been diagnosed with X and his symptoms are X. Based on a lab value of X, what would you do first?
You see, it's not enough that you know what diagnosis X is, or what symptoms are present, or even the lab value. You have to know how to apply it to that patients particular situation, which change depending on diagnosis, symptoms, and lab values. They will offer you answers that might all sound good, but the key phrase is "What will you do FIRST", meaning you have to know that information inside and out!
Keep plugging away at it. All you can do is your best. Check out those links from Daytonite--she's a grand master at finding extremely useful information.
P.S. The above poster who mentioned going over your test and finding out why the answer you gave were wrong is great advice. It will also give you insight into how your instructor thinks and what they think is important for you to know. Please take advantage of that option.