Formative research uses qualitative and quantitative methods to provide information for researchers to plan intervention programs. Gaps in the formative research literature include how to define goals, implementation plans, and research questions; select methods; analyze data; and develop interventions. The National Heart, Lung, and Blood Institute funded the Trial of Activity for Adolescent Girls (TAAG), a randomized, multicenter field trial, to reduce the decline in physical activity in adolescent girls. The goals of the TAAG formative research are to (a) describe study communities and schools, (b) help design the trial's interventions, (c) develop effective recruitment and retention strategies, and (d) design evaluation instruments. To meet these goals, a variety of methods, including telephone interviews, surveys and checklists, semistructured interviews, and focus group discussions, are employed. The purpose, method of development, and analyses are explained for each method.