Background and theory. Adolescent development ; Millennials ; Serving diverse teens ; Information-seeking behavior ; Developmental assets ; Youth participation ; The whole library experience -- Planning. Developing effective goals and objectives ; Outcome measures ; Collecting data : types and sources. User data ; Usage data ; Policies and procedures ; Program data ; Budget data ; Facilities data ; Function data ; Staffing data ; Finding data -- Implementation. Raw data : what does it mean? Statistical data ; Evaluating policies and procedures ; Competencies ; Using data to make changes. Changing priorities ; Using data to support your case ; Using data to plan for the future -- Evaluation. Evaluation as a decision-making and communication tool ; Outcome-based evaluation ; Evaluating YA collections ; Evaluating teen summer reading programs ; Evaluating teen programs and special events. Informal evaluations ; Formal evaluations ; Focus groups ; Evaluating staff -- Best practices. What an excellent teen services program looks like ; Using the YALSA competencies ; Using the YALSA teen services evaluation tool. How library administrators can use the evaluation tool ; How trustees and governing bodies can use the evaluation tool ; How library patrons and community members can use the evaluation tool ; How library and information science faculty can use the evaluation tool ; How teen services librarians can use the evaluation tool -- References and resource guide. Links and books ; Sample forms. Needs assessments ; Summer reading programs ; Program evaluation ; Staff evaluation ; Checklists ; YALSA's competencies and evaluation tool. YALSA's competencies for librarians serving youth : young adults deserve the best ; YALSA teen services evaluation tool.