Although healthy lifestyles (HL) offer a number of health benefits, nonadherence to recommended lifestyle changes remains a frequent and difficult obstacle to realizing these benefits. Behavioral counseling can improve adherence to an HL. However, individuals' motivation for change and resistance to altering unhealthy habits must be considered when developing an effective approach to counseling. In the present article, we review psychological, behavioral, and environmental factors that may promote adherence and contribute to nonadherence. We discuss two established models for counseling, motivational interviewing and the transtheoretical model of behavior change, and provide an example of how these approaches can be used to counsel patients to exercise and increase their levels of physical activity.