A Yes culture: Ask team members to catch out each when they hear "yes but" and ask how to convert it to "yes and..."
When decisions are being weighed, ensure that the benefits are listed first, rather than the costs or problems. Agree to spend twice as much time focused on possible solutions than on restating the problem.
Experimentation: The team needs to be constantly experimenting with new ideas, new ways of working, new relationships. Try counting the current experiments and review how they could be doubled in number.
Constructive disagreement: Play Devil's Advocate. Get people in the team to challenge an accepted point of view from an alternative perspective.
Set up 'trials' or 'speaker's corner'- where different members of the team take different positions on some issue and see which makes the best case for a line of action.
Building on ideas: Establish a group norm in which an idea put forward must be heard with respect, and the first action by everyone is to see how it could be made to work.
Look for a truthful statement that contains apparently conflicting ideas about your current situation. For example: "We agree to disagree", "The only constant in our situation is change", "we have to slow down to speed up." Use these to explore what they reveal about team performance.
Permission to fail: Act out a post-mortem at the start of a project - imagining the worst. Pretend the team has failed. What are the implications?
When a team member fails at something, offer public acknowledgement for the fact that at least they tried. And then look for the lessons to be learnt.