Set up a 'retrospective mailbox' at the beginning of the iteration. Whenever something significant happens or someone has an idea for improvement, they write it down and 'post' it. (Alternatively the 'mailbox' can be a visible place. This can spark discussion during the iteration.) Go through the notes and discuss them. A mailbox is great for long iterations and forgetful teams.
Create actions based on how much control the team has to carry them out Source:
Diana Larsen who adapted it from 'Seven Habits of Highly Effective People' by Stephen Covey and Circle of Influence and Concern' by Jim Bullock
Prepare a flip chart with 3 concentric circles, each big enough to put stickies in. Label them 'Team controls - Direct action', 'Team influences - Persuasive/recommending action' and 'The soup - Response action', from innermost to outermost circle respectively. ('The soup' denotes the wider system the team is embedded into.) Take your insights from the last phase and put them in the appropriate circle. The participants write down possible actions in pairs of two. Encourage them to concentrate on issues in their circle of influence. The pairs post their action plans next to the respective issue and read it out loud. Agree on which plans to try (via discussion, majority vote, dot voting, ...)
Prepare 3 flip chart papers titled 'Helped', 'Hindered', and 'Hypothesis' (suggestions for things to try out). Ask participants to help you grow and improve as a facilitator by writing you sticky notes and signing their initials so that you may ask questions later.