To pass a test, anyone has to study using a text-book, absolutely no-one can "pre-train" for something without having a textbook, unless we consider "out-of-water web-directions" to be appropriate textbook-quality material.
If you have a like-minded buddy who already went through one of the classes, you won't be seeking web-directions, as they will, most likely, tell you about your trim and control in the water. Best advice: try to reach out, meet and dive local DIR-minded community
Coming back to the original question of the things to prepare, I would repeat some of the advice posted before: make sure you are comfortable with whatever rig you are diving, specifically, try to think a bit about your trim every time you are in the water. The only thing, I would advice to work for on in the water before the class is buoyancy.
Repeating myself, buoyancy and trim are essential. If you can obtain perfect control of these two basic, but challenging, in-water concepts, no kind of task-loading skill sessions, introduced during the Fundamentals course, will get you off the correct path towards mastering the skills taught in class. I am pretty positive that it is not the new skills that prevent anyone from passing, but lack of proficiency in these two basic concepts that does.
For those who are still "pre-training" for the class and consider 3 foot buoyancy window too big, establish 1 foot buoyancy window and try to stay within it - I can't.
A bit arrogant point, but I, as all of us, do love and value my life: Those that consider the transportation and course fees too expensive, I would advise to think about the value of one's life to you, your family, and people you care about. Do you think that arranging another relatively expensive session with quality instructor is not worth your life? When something bad is going to happen underwater, whether in 3 feet or 100 feet of water, the card and a pass won't be useful at all, but the skills that you obtained during the extra sessions with the instructor may save one's life. And if you think that you already know enough, and won't learn more from an instructor who is, at least, Tech 1 certified (and most of them are more) - you are truly wrong.
IMHO: I bet that an instructor will know whether a student will be able to pass the Fundamentals class during the first 30 seconds under water, without even doing any skills.