The good people at the Center for Social Media have published a Code of Best Practices in Fair Use for Online Video. Here’s what they say about it:
This document is a code of best practices that helps creators, online providers, copyright holders, and others interested in the making of online video interpret the copyright doctrine of fair use. Fair use is the right to use copyrighted material without permission or payment under some circumstances.
This is a guide to current acceptable practices, drawing on the actual activities of creators, as discussed among other places in the study Recut, Reframe, Recycle: Quoting Copyrighted Material in User-Generated Video and backed by the judgment of a national panel of experts. It also draws, by way of analogy, upon the professional judgment and experience of documentary filmmakers, whose own code of best practices has been recognized throughout the film and television businesses.