This manual, intended for the librarian or information specialist beginning with online systems, introduces the National Agricultural Library's (NAL) Cataloging and Indexing System (CAIN) and presents the search techniques required for retrieving information on agriculture and its many related fields. The manual, which concentrates on the online mode of accessing the CAIN data base, discusses the basic strategies employed in constructing search strategies for online literature retrieval and the fundamentals of establishing computer communications; provides information about the CAIN unit record and cataloging and indexing practices followed by the NAL staff; and details information about access to the CAIN data base, including access with the DIALOG system of Lockheed Retrieval Service and through the ORBIT system of System Development Corporation. (Author/CWM)