In this chapter, we synthesize evidence on the two dominant error classes—perceptual and cognitive—and offer practical countermeasures. One countermeasure is mastery of anatomic attachment sites and common anatomic variants; this helps prevent both misses and overcalls. Checklists and universal differential frameworks are also countermeasures; they help us “expect the unexpected”. By combining these countermeasures with simulation-based learning, feedback loops, and a growth mindset, radiology teams can enhance diagnostic accuracy, patient safety, and the value of diagnostic imaging.