An ideal sample is the one that can best answer your hypotheses or research questions, and this chapter describes how ethically to select and protect such participants. Multiple random and nonrandom sampling procedures are compared and contrasted in terms of feasibility, methods, and how well they represent a larger population to whom you want to generalize study results. Subject eligibility criteria, sample size, vulnerable subjects, benefits and risks to subjects, and how to handle subject withdrawal are covered. Elements of informed consent—information disclosure, subject comprehension, and voluntary participation—are emphasized, and an editable consent script provided. Additionally, questions in a referenced Protocol Worksheet facilitate gathering information to write relevant IRB protocol sections. The requirement to attach verbatim copies of initial and follow-up recruitment materials as protocol appendices is noted.