I just took the test (and passed!) in October. One thing I found out is that the questions in the ABA study guide are harder than the questions on the test. Those test questions in the study guide had me in a bit of a panic. Another important tip, don't wait until the last minute to study!
Something else which probably goes without saying is to really concentrate on the rules and regs that you don't normally have to deal with, as Andy mentioned.
And another thing that was probably just due to how I learn and study, I had some difficulty at first studying from the outline format in the study guide. I guess I was just used to the narrative form of the regs. But, once I got used to the format, I found it to be a good way to study. And, now that the test is behind me, I also found that the outline format is a great reference when you need to find a quick answer without having to dig into the text of the reg.
Good luck!