Meet in a big group. Set the rules: Make a time limit for the session. Decide to make no decisions. Write down every idea, no matter how small or silly.
Each participant brings one idea on a strip of paper and puts it in a bowl upon entering the room. Read these first.
Each participant writes down five ideas and submits the list to a moderator. Ideas are read aloud anonymously. The top three ideas are chosen according to which get the best reaction from the group. Break into small groups and work with the three ideas to see if they can be taken further.