Most administrator training programs focus on what educational leaders should do rather than what they should not do. To help administrators in their roles, an overview of mistakes to avoid is offered in this ERIC digest in Spanish. The emphasis on the negative stems from the belief that undesirable behaviors are far fewer than desirable ones. The digest reviews the types of mistakes leaders tend to make, identifying 15 categories of errors, with most of them arising from poor human-relations skills. Many leaders fail to provide their staffs with adequate encouragement, or they make decisions based on a poor understanding of their schools' issues and problems. The second most frequently occurring mistake falls under the category "poor interpersonal communication skills," especially the failure to listen. These interpersonal problems are worsened by principals' failure to give and receive feedback. Since interpersonal skills and human-relations skills are closely associated, it is argued that by building future principals' human-relations skills, these leaders' interpersonal competence will also improve. The digest concludes with a list of six suggestions designed to help principals avoid career-ending mistakes. (RJM)