This short video, produced by The Ohio State University Libraries, provides a good example of how to do a fair use analysis.
The fair use exemption is most likely the exemption that most educators and scholars are familiar with. It is codified in Section 107 of the US copyright law and states:
". . .the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include--
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors."
For a basic overview, take a look at Fair Use Fundamentals, a summary document commissioned by the Association for Research Libraries. Fair use is a balancing act and is highly dependent on the facts in each situation. All 4 factors must be considered in any fair use analysis -- none is more important than the other. Any parameters that have evolved around fair use have been the outcomes of court decisions. Many institutions have developed checklists to guide users through fair use analysis. Regarding the two such tools identified below, one was developed at Baylor University and the other is an interactive tool developed by the American Library Association:
Two important concepts to be considered in any fair use analysis are "transformation" (1st factor) and "heart of the work" (3rd factor):
Although there are no clear, bright lines associated with fair use, a number of organizations have developed guidelines or best practices, which are available from the Center for Social Media:
The creators of these best practices investigated how educators and scholars in the specific environments fairly use copyrighted content and from those environmental scans they identified the practices that were most common among all of them to develop the disciplinary-specific guidelines.