As others have mentioned, the Proprietary Lease, By-Laws, and House Rules are fundamental (but dry) reading. Going through recent meeting minutes is also a good idea. For more interesting reading, the Habitat archive is a gold mine. Habitat is the *only* magazine I read cover-to-cover every month.

Also, don't be shy about asking a more experienced board member to sit down with you and talk about how things work. Then Google some articles on "What is a Co-Op?" and that sort of thing.