The best way to get a meaningful result out of the Retrospective is by being prepared. Here are a few pitfalls which indicate your Retro should be prepared better:
Lack of purposeMany teams focus on the ceremony itself "because the Scrum guide says so" without comprehending the basic purpose. Much more important than how, where or when a Retro is conducted is the "Why". As mentioned before, the purpose of a Retro is driving the Continuous Improvement. Even before the team enters the room, they should be energized with the idea to drive change.
The Scrum Master can help build this energy level during the entire Sprint, but also by facilitation throughout the ceremony.
Whimsical inputSome people will only start to consider the Retro when it begins. Improvement potential unearthed during the Sprint is forgotten, they make up something in the heat of the moment just to have said something. This adds complexity to the Retro and may distract from valuable topics. A good way for the Scrum Master to counter this is by setting up an "Impediment Board" and encouraging people to add their impediment items throughout the Sprint. We can then bring this board to the Retro and simply start asking "Now - what?"
No pulseEspecially Scrum Masters sharing multiple teams often fall into the trap of not having taken a pulse for the Retro. Not knowing what is the perspective of the team, they need to waste precious Retrospective time fishing in troubled waters, trying to uncover an issue. Effectively, this is the Scrum Master's equivalent to "Whimsical input": Whimsical facilitation. The best way for the Scrum Master to get a pulse is by silently observing throughout the sprint and giving individual team members to speak up over a cup of coffee in a 1:1 setting.
ConclusionRetrospectives have a clear, unique and very important purpose of introducing process, structural and organizational change to improve the team.
To get the most out of your Retrospectives, everyone should be well prepared.