How to run a productive meeting?

Have a written agenda (provided before the meeting, of course)

No "Lets talk about the service architecture" nonsense. Provide the exact details of what the outcome of the meeting should be. Even been lucky enough to cancel meetings when the agenda points are answered in a reply email. Its awesome.

As conditioned as we are about agendas, a few mgrs still skip the agenda and it ends up as you would imagine. At the end, everyone is like "Why are we here? What did we decide? Looks like we need another meeting..."