Everything you will need to know will be explained on the first day, just relax and listen.
There is nothing special you need to know before hand and the class is only as difficult as you deem it. Pay attention, ask for clarification, read the book, and do the assignments.
Aidan, i agree with John. if you have good instructors, class will flow good and be easy to follow. AFTER the class...find a highly recommended test prep web site and start taking practice tests. there are many sites...just don't get caught up in ones that want you to pay lots of money. enjoy your class and ask lots of questions.