In order to direct and monitor CIs, it is necessary to understand their motivating factors such as money, revenge, elimination of competition, fear, self-aggrandizement, prosecutorial or judicial leniency, and repentance. Although investigators are encouraged to develop a trust-based relationship, they should be aware of potential problems resulting from lying, double-dealing, rip-offs, and blackmail to prevent significant risk to the integrity of the investigation and officer safety. A particular recommendation concerns maintenance of a file on informants' activities. Other topics covered include legal use of informant information; problems for the agency, supervisor, and investigator; and uses for an informant file system. Guidelines are provided for determining key elements of an informant file system, using informants, using unreliable informants, and securing CI files.