Quotes from Karl Wiegers

If possible, quantify the contribution the feature makes towards the business objectives, so that people can make scoping decisions on the basis of facts rather than emotions ([ref013]). Will a specific feature contribute roughly $1,000, $100,000, or $1,000,000 toward a business objective? When an executive requests a new feature that he thought of over the weekend, you can use quantitative analysis to help determine if adding it is the right business decision.

I'm not that crazy about reality, but that's all I've got.

Assign someone who isn't actively participating in the discussion to be the scribe, responsible for taking accurate notes. Session notes should contain an attendee list, invitees who did not attend, decisions made, actions to be taken and who is responsible for each, outstanding issues, and the high points of key discussions.