Because Agile stresses the importance of continuous improvement, having a regular Agile retrospective is one of the most important of Agile development practices.
"Regardless of what we discover, we understand and truly believe that everyone did the best job they could, given what they knew at the time, their skills and abilities, the resources available, and the situation at hand."
Set the stage - get the team ready to engage in the retrospective, perhaps with a warm-up activity
Gather data - create a shared picture of what happened during the retrospective
Generate insights - discuss what was successful and identify any roadblocks to success
Decide what to do - identify highest priority items to work on and put measurable goals on those items so they can be completed (15 minutes)
Close the retrospective - reflect on the retrospective and how to improve it, and to appreciate accomplishments of the team and individual interactions
• What are the positive things about this iteration? (1 min.)
• What are the negative (minus) things about this iteration? (1 min.)
• What was interesting about this iteration? (1 min.)
If you are doing a 5 times why retrospective you can ask “Why did something happen?” or “What caused it?” (if you prefer not to use the “why” word) to get to the root causes of problems.