The Agile Manifesto starts off with:

We are uncovering better ways of developing software by doing it and helping others do it.

(Source: http://agilemanifesto.org/)

And the 12 Principles behind it end with:

At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.

(Source:http://agilemanifesto.org/principles.html)

Agile at its core is fundamentally about adapting to changing circumstances. There is no single “right way” to do things that is always correct in all circumstances. Accordingly, agile teams need to spend some of their time getting better at the process of delivery, in whatever ways work for that team in that circumstance.

The Retrospective session is the key to this.

In addition to the very good advice found here, my keys to Retrospective success are:

• Make sure that all dedicated team members attend
• Only allow the dedicated team (and a facilitator) to attend (no visitors or observers)
• Provide a private space so people can speak freely
• Emphasize that this is a safe space so people can speak freely
• Remind the team to assume positive intent