Safety initiatives in hospitals should focus on common health care interventions that when used appropriately can improve important health outcomes, and when used inappropriately or not at all, result in substantial harm. We suggest that errors of omission should be a safety priority. We focus on preventive health care interventions, and describe five steps that can improve patients' safety by changing clinician behaviour. The steps are to: do an environmental scan; understand current behaviour, target behaviour for change (why, what, when, where, and who); adopt effective strategies to change behaviour; and synergise.