Approval plans are used by many libraries as an adjunct to title-by-title selection, and sometimes as a substitute for it. The author examines this approach to purchasing library materials, considering positive and negative effects approval plans may have on collection balance as well as on acquisitions budgets and workflow. The article also serves as an introduction to approval plans for entry-level acquisitions librarians, library school students, and paraprofessional library staff. Practical concerns in setting up approval plans are discussed, such as approval plan profiling, plan maintenance, and evaluation. Budget and accounting considerations are introduced. Although approval plans are widely used, new librarians may have learned little about them in library science courses. The approval plan is presented as a useful tool for shaping and maintaining library collections.