A full-mouth rehabilitation should be correctly planned from the start by using a diagnostic wax-up to reduce the potential for remakes, increased chair time, and laboratory costs. However, determining the clinical validity of an extensive wax-up can be complicated for clinicians who lack the experience of full-mouth rehabilitations. The three-step technique is a simplified approach that has been developed to facilitate the clinician's task. By following this technique, the diagnostic wax-up is progressively developed to the final outcome through the interaction between patient, clinician, and laboratory technician. This article provides guidelines aimed at helping clinicians and laboratory technicians to become more proactive in the treatment planning of full-mouth rehabilitations, by starting from the three major parameters of incisal edge position, occlusal plane position, and the vertical dimension of occlusion.