Strategies counselors can use to involve "significant others" (persons who have an important influence on the career plans of students, e.g., parents, peers, and relatives) in high school career guidance programs are offered in this handbook. Content is presented in three main sections: (1) a brief, nontechnical section summarizing how significant others outside the school help to influence students' career plans; emphasis is also on the overall societal context within which the process of significant others influence operates; (2) discussions of strategies that school personnel may use to incorporate significant others into the career guidance program, e.g., methods for identifying individual students' significant others, and suggestions for using communication media for involving significant others in career planning; and (3) an outline of the elements that may be included in a student career planning file, such as aptitudes and interests inventories, employment opportunities, and preparation requirements. An annotated list of resource materials and an open-ended attitudinal questionnaire (concerning the student's feelings about career plans) are appended. (TA)