Assume that it's all possible. Besides, you're just playing. Don't write the words in list form, but randomly all over the page.
One specific strategy for getting supportive ideas is to request a meeting with a few key people on whose ideas and enthusiasm you can count.
This isn't really a phase, but an attitude that must permeate each of the other four phases. If you're not having fun along the way, stop and reconnect with your purpose.
