The best website about retrospectives on the entire internet ever is retrospectives.com, it just says it all.

I send a link to retrospectives.com together with the invitation to the meeting to set the purpose and the expectations.

What is a retrospective? From the site:

A retrospective is a ritual gathering of a community at the end of a project to review the events and learn from the experience.
No one knows the whole story of the project. Each person has a piece of the story. The retrospective ritual is the collective telling of the story and mining the experience for wisdom.

What you get after the meeting is a nice list of meeting notes and happy people, and if that isn’t enough these are the 3 main reasons why I do it:

1. regardless of how the project went, the lessons learned are always valuable for the people on the team, like the definitions says, it’s mining experience for wisdom and will help people grow
2. you are creating a valuable project management asset for future risk assessment
3. it’s an official point in time that says the project is actually done and that’s cool because everybody likes the feeling of accomplishment (or relief )

When you want to do this, all you need are the 4 questions from retrospectives.com to set the correct mood. Although it’s kind of tempting, I’m not going to copy the entire retrospecitives site, so head over there.

I got this via the unofficial bridge king of the West and delivery manager at Nascom, Tom Tabruyn.