Fair+Use+Guidelines

Four things are considered when determining fair use: FBI Fair Use Reminder  HOW CAN I GET PERMISSION TO USE COPYRIGHTED MATERIAL? You can ask for it. If you know who the copyright owner is, you may contact the owner directly. If you are not certain about the ownership or have other related questions, you may wish to request that the Copyright Office conduct a search of its records or you may search yourself. See the next question for more details.
 * The Purpose of the Use
 * The Nature of the Copyrighted Work
 * The Amount or Percentage of the Work Used
 * The Effect of the Use on the Original Work

INTERESTING SET OF GUIDELINES: http://owl.english.purdue.edu/owl/resource/731/1/

SOURCES "U.S. Copyright Office - Fair Use." //U.S. Copyright Office//. N.p., n.d. Web. 11 Jan. 2011. <http://www.copyright.gov/fls/fl102.ht