Choosing the right treatment for the patient requires that the right diagnosis is made first. In primary and ambulatory care, however, diagnostic errors are both common and commonly preventable. The World Health Organization has recommended that all health professionals should receive formal training in the principles of diagnostic reasoning and the causes of diagnostic error, and that strategies and interventions to reduce the risk of diagnostic error should be used in clinical practice. This article describes a mnemonic checklist, SAFER PRACTICES, which can be used in an integrated approach to the prevention and detection of diagnostic errors that starts in the classroom and continues through to the consulting room.