This article is intended to serve as a practical guide for practitioners interested in incorporating evidence-based diagnosis (EBD) instruments into their clinical practices to refine the diagnostic process. Three measures are used to illustrate this process, the DISC-IV (Shaffer et al., 2000), the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime version (K-SADS-PL) (Kaufman, et al., 1996), and the Achenbach System of Empirically Based Assessment (ASEBA) School-Age Forms (i.e., the Child Behavior Checklist, the Youth Self-Report Form, and the Teacher's Report Form; Achenbach and Rescorla, 2001). The purpose of this article is not to advocate for incorporation of these specific measures into clinical practice but rather to provide interested practitioners with useful information to make decisions about what form of EBD may be most appropriate for their own practice settings. Guidelines are provided for practitioners, including suggestions for identifying instruments, examining the evidence in support of those instruments, evaluating the feasibility of using those instruments in clinical practice, and implementing them.