Place a circle or sphere in the middle of a free space. Let the team gather around it. Explain that the circle is the center of approval: If they agree to a statement they should move towards it, if they don't, they should move as far outwards as their degree of disagreement. Now read out statements, e.g.
I feel I can talk openly in this retrospective
I am satisfied with the last iteration
I am happy with the quality of our code
I think our continuous integration process is mature
Watch the constellations unfold. Afterwards ask which constellations were surprising. This can also be a closing activity (#53).
Visualize how information flows in, out and around the team Source: Tarmo Aidantausta
Is information not flowing as well as it needs to? Do you suspect bottlenecks? Visualize the ways information flows to find starting points for improvements. If you want to look at one specific flow (e.g. product requirements, impediments, ...) check out Value Stream Mapping (#79). For messier situations try something akin to Cause-Effect-Diagrams (#25). Look at the finished drawing. Where are delays or dead ends?
Prepare a flip chart with 3 columns titled 'What', 'Who', and 'Due'. Ask one participant after the other, what they want to do to advance the team. Write down the task, agree on a 'done by'-date and let them sign their name. If someone suggests an action for the whole team, the proposer needs to get buy-in (and signatures) from the others.
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.