American University's Program on Information Justice and Intellectual Property has released the Code of Best Practices in Fair Use for Online Video.
Here's an excerpt from the "Introduction."
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. . .