I wouldn't get too far ahead of class. It will make much more sense if you read it, hear a lecture, do an exercise, see it from different angle and study for a test on a topic.
The main things you definitely could do to prepare are (from my experience) study up on definitions, like what does ALS mean..."Advanced Life Support"...what does Q stand for..."Every"...etc...
Google EMS definitions or acronyms or whatever.
Also, EMT basic is just basic life support. In essence, it is really, really good CPR and first aid. Even if you have already taken a CPR for the professional rescuer, it would seriously be worth it to take it a second time somewhere else and see what else you can learn about it.
Download podcasts on the ABCs: Airway, Breathing and Circulation.
The people in my class that failed either the final, practicals or the National Registry, all, in my opinion, very obviously didn't have a very good grasp on CPR and the ABCs. This was especially evident in practicals. If you're trying to recall DCAP-BTLS, and such under stress, dealing with a trauma, but you don't have good ABC fundamentals, you'll forget something über important, like high-flow O2.
