I used the OAT CDs when doing my exams, and I found them particularly helpful as a get-up-to-speed on a topic, then read the books and went back to the CDs for brushup after some confuser bashing.
The CDs are particularly helpful for topics which benefit from a visual explanation such as nav/met/radio aids etc - the animations and examples certainly made it easier to understand than the (sometimes) dry explanation in the Thoms for example.
Basically - get hold of as much study material as you can, and learn, learn, learn. And the first thing you do - learn how to use the whizz wheel!