Make sure that you go into it with the right attitude. I've heard of instructors recently—and quite rightly—failing people for not giving the impression that they understand the gravity of the role and all it entails. It sounds as though you do care though, so that shouldn't be an issue, it's more to catch people out whose only motivation is the prospect of extra overtime and couldn't care less about keeping people safe.
I'd also make sure that you have a copy of the rulebooks to hand, they are available on the RSSB website (I believe these days you need a free account to access them). They should cover everything you need to know on the course, but if there's anything you're struggling with or think might be confusing have a look through the rulebooks, and if it's still not clear ask them to clarify the next day. It's definitely worth having an extra read of things that you haven't seen done very often/at all (e.g. for me this would be token, TCOD and signalling disconnections as they're never done in my area).
For the test at the end, make sure that you read the question properly and answer all the questions. Watch out for the similar ones that are easy to confuse, especially working in a possession inside a worksite and in a possession outside a worksite as that's a common thing to get tripped up on. My technique is to answer them all, marking off which I'm not 100% sure of, and then go back through them all, paying particular attention to the ones I was uncertain of. On the first pass through I pick the right answers, when I'm checking I mentally cross off the wrong answers ("That's nonsense, that's nonsense, that's nonsense, to THAT must be right").
Good luck, and feel free to drop me a line if there's anything you can't wrap your head around, I'll always do my best to help.
