Identifying and fully collecting relevant evidence in the early stages of an investigation is critical to success. Improperly collecting evidence will, at a minimum, result in an embarrassing and difficult process of corrective efforts as well as wasted time. At worst, an improper collection will result in working with the incorrect set of data. In the latter case, court sanctions, lost cases, and ruined reputations can be expected. This chapter provides the guidance to ensure all relevant data is identified, so these situations do not occur.