[This post is part of Corinna’s Guide to Facilitating Retrospectives]
‘Ello!
One of the main goals of a retrospective is to build shared understanding. That every participant contributes their unique perspective on events – things they observed and how they interpret them.
For this to happen, you need open conversations and those need trust from everyone involved. Trust that they won’t be blamed and trust that what they share will stay within the group.
That’s why some facilitators read out both the Prime Directive and the Vegas Rule in the beginning of every retrospective to remind everyone.
Prime Directive
The Prime Directive (for retros, not Star Trek) was created by Norman Kerth (the godfather of retros – we owe him) to remind everyone to stay collaborative, constructive and focussed on the way forward rather than blame:

The thing is, we can’t change the past. But we can influence the future. Results are better if we stay curious rather than become accusatory – in retrospectives and most other situations in life as well.
(If you don’t like the specific wording of the Prime Directive, you’re not alone. Google for one of the many alternatives or come up with your own. Take care to keep the spirit intact!)
The second common ground rule is the
Vegas Rule
“What happens in Vegas, stays in Vegas”
To enable candor and high levels of trust, retrospectives are confidential. You want people to openly share their thoughts. That is less likely to happen if they are afraid to feed the rumor mill. Be very careful how you use information gained during retrospectives outside of them. The only information that is okay to share outside of the retrospective are its action items.
Of course just reading these rules out will not turn an “unsafe” environment into one where people suddenly feel comfortable sharing. You might need to work on Psychological Safety first. It will help you create conditions for fruitful retrospectives:


Time to take a minute:
What’s the vibe in your team at the moment? Do you openly share information or are people guarded? How high do you think the Psychological Safety is? Are you happy with the current state?
May your retros always be high on trust and low on blame,
Corinna
PS: Did you know there's a Retromat eBook Bundle? Ready-made retrospective plans for beginners and all activities from Retromat for experienced facilitators. Check out the Retromat books