A Guide to Human Intelligence (HUMINT)

This article provides a very good overview of all aspects of HUMINT.  Note the discipline is multi-faceted with overt and clandestine capabilities.  The overt capabilities (law enforcement informants, witnesses, liaison services, debriefings, diplomats) are far more useful (for day-to-day intelligence) than their clandestine counterparts.  However, clandestine intelligence can be very useful in specific situations.  Clandestine collection may be turning into a dinosaur (or at least changing dramatically) in a world with biometrics, ubiquitous sensors, visual surveillance systems, and Artificial Intelligence to put it all together