I have summarized some of the methods to overcome and defeat Groupthink during a brainstorming session:
Few best practices include below methods:
Engage in Open discussions
Allocate a “Devil’s Advocate” in the team - Red Teaming
Structure the brainstorming session
Encourage Wild Ideas
Evaluate alternatives cautiously - Use "Six Thinking Hats" approach
Disrupt abundantly when required
Encourage Conflict of ideas, so that group doesn’t ends up with limited decisions
Give everyone chance to speak up, during the session, may be in a Round-Robin fashion timely
Add new elements to Brainstorming à Introduce “Reverse Brainstorming”; “Brainwriting”
Give more attention to Group Dynamics
Encourage Diversity
Occasionally, Invite Cross function team member as external consultant
Remain to be Impartial until to wrap up