Dress for success. Think of boating the same way you would prepare for a full contact sport like football. You wouldn't play football without head protection, the same is true for whitewater boating. I also recommend "Dress to Rescue". Some rescue situations require swimming in cold water. Paddling with a dry top instead of a dry suit in the Winter works fine until you swim or need to get in the water. Rescue work requires special equipment like throw ropes, carabineers, and sometimes a rescue vest.
If you are taking this course, you probably have some experience in your canoe or kayak and have suitable gear for most day trips. You may be considering more advanced whitewater and want solid rescue and accident avoidance skills. Rescue work does require some special equipment that you hopefully are not required to use on every trip. Some great examples are throw bags, carabineers, rescue knife, etc. You probably should examine your present boating equipment to ensure it is still in good shape - what good is a dry suit with torn gaskets. For the most part, we will be concentrating on rescue gear. Here is a nice introduction video on various rescue equipment: Sample Rescue Gear.