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.
Each team member explores one topic in depth in a series of 1:1 talks Source:
Each participant writes down one topic they want to explore, i.e. something they'd like to change. Then form pairs and spread across the room. Each pair discusses both topics and ponders possible actions - 5 minutes per participant (topic) - one after the other. After 10 minutes the pairs break up to form new pairs. Continue until everyone has talked to everyone else. If the group has an odd number of members, the facilitator is part of a pair but the partner gets all 10 minutes for their topic.
Asking and answering go around the team circle - an excellent way to reach consensus Source:
Everyone sits in a circle. Begin by stating that you'll go round asking questions to find out what you want to do as a group. You start by asking your neighbor the first question, e.g. 'What is the most important thing we should start in the next iteration?' Your neighbor answers and asks her neighbor a related question. Stop when consensus emerges or the time is up. Go around at least once, so that everybody is heard!
Let team members appreciate each other and end positively Source:
Agile Retrospectives who took it from 'The Satir Model: Family Therapy and Beyond'
Start by giving a sincere appreciation of one of the participants. It can be anything they contributed: help to the team or you, a solved problem, ...Then invite others and wait for someone to work up the nerve. Close, when no one has talked for a minute.