very good advice here from dsmitch19. I hope everyone studying reads it.
as said previously, "...for Dummies" helps you pass. It can help with your organization and with answering all aspects of the question. but without going beyond what Al says you won't get a great score.
I grade these things, and see people spent maybe up to 70% of a full page writing A/A/F/M for "three styles" questions, and then barely say anything in the distinguishing characteristics section. The former is 40%, the latter 25% - use your time wisely. Along with a classic example, everyone should be able to come up with a unique and meaningful sentence describing every substyle from the Overall Impression, History, Comments, and Ingredients sections of the Style Guidelines. And no, saying BoPils was created in 1842 is not enough.
On a similar note, don't expect a lot of help from your grader if the only thing you wrote for "similarities" between Munich Helles, Octoberfest, and Vienna was that they were "all German lagers."
(however, noting they are all lagers as a similarity and the two different countries of origin as a difference would get you some credit. but give me more! - It's 25% and you can get it quickly!)