Sometimes people say, that for ACTs, one needs a specific knowledge of how to take the test, which does not teach you anything, but I did not get the feeling.
All of the questions seemed quite reasonable, no tricks and not even a need for smart ideas (unlike let's say math Olympiad). Basically know the basic math rules, and you'll be fine.
The knowledge I've gained at a Czech Gymnasium with more traditional methods (i.e. no multiple choice) translated very well into getting a good score.