Make it fun!
It's not enough to finish a project on time and within budget. A project is only a true success if your customer enjoyed the design and construction process. Right? Can I get an amen?
Design meetings are work sessions, but they are also a place to educate user groups. I like to get doctors geeked up about air changes. I'll explain sound control measures to teachers. Also, there's no reason cupcakes shouldn't be served. Everyone should leave the meeting feeling smarter and a little jacked up on chocolate frosting.