Hand out pens and sticky notes. Ask everyone for ideas on how to turn the next iteration / release into a certain desaster - one idea per note. When everyone's finished writing, hang up all stickies and walk through them. Identify and discuss themes. In the next phase turn these negative actions into their opposite.
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.