As an introduction to the use of the DIALOG online retrieval service, this guide presents material that was developed during a fellowship at Carlos III University, School of Library Science and Documentation, Madrid (Spain) and that is based on a course on the same subject taught in English at Texas Women's University. Although the use of DIALOG presupposes a knowledge of English, this guide is presented in Spanish for the convenience of its intended audience. In addition, DIALOG is constantly improving its software and the details and recommendations here are based on the software available in April 1994. The lessons cover (1) online information retrieval; (2) databases; (3) production, structure, and organization of databases; (4) determination of the user's objectives through interviewing and beginning the online search; (5) the search process; (6) DIALOG rules; (7) rules and techniques for DIALOG searches; (8) online searching as a communication process; (9) characteristics of languages and their effectiveness in retrieval; (10) retrieval and indexing; (11) evaluation of search effectiveness; (12) types of search strategies; and (13) DIALINDEX and OneSearch. Appendixes contain possible final examinations, transparencies, practice exercises, and instructions for connecting to DIALOG. (SLD)