Physicians use heuristics or shortcuts in their decision making to help them sort through complex clinical information and formulate diagnoses efficiently. Practice would come to a halt without them. However, there are pitfalls to the use of certain heuristics, the same ones to which humans are prone in everyday life. It may be possible to improve clinical decision making through techniques that minimize biases inherent in heuristics. Five common clinical heuristics or other sources of cognitive error are illustrated through neurological cases with missed diagnoses, and literature from cognitive psychology and medicine are presented to support the occurrence of these errors in diagnostic reasoning as general phenomena. Articulation of the errors inherent in certain common heuristics alerts clinicians to their weaknesses as diagnosticians and should be beneficial to practice. Analysis of cases with missed diagnoses in teaching conferences might proceed along formal lines that identify the type of heuristic used and of inherent potential cognitive errors. Addressing these cognitive errors by becoming conscious of them is a useful tool in neurologic education and should facilitate a career-long process of continuous self-improvement.