looking for an activity?

So you are looking for a retrospective activity. Let me try to help.  Please follow the links.

Retrospective stages: the beginning -> the middle -> the end.

Are you planning something more like a futuro-spective?

Is this one driven by a timeline?

Do you need to shake things up to start with (energizers)?

Have you considered driving your retrospective by feelings?

Are you preparing a retrospective for a distributed team?
Is this the very first retrospective for the team? If yes, consider running some norming activities. Norming activities should help identifying activities, processes and ways the team members will interact. 
Are you looking for some ideas on how to sequence your retrospective activities?