For those who completed Medical Coding & Billing?

I took a small online class, got the basics of Medical Coding. I can pretty much code ALMOST anything, but sometimes it gets complicated. Anyway, I was wondering if its important to know all of the billing information from the textbook and all the acts, and also if terminology is a must. I took terminology, too, but a lot of it just doesn't stick. What are the things I absolutely MUST know?? Details about the ICD-9-CM and the CPT Manual would be great. The E & M codes get me sometimes though. Thank you!