How to Maintain the Right Kind of Energy in a Structured Meeting?

I know that a lot of, especially start up organizations, really enjoy that sortof adhock one to one around the coffee pot. How did you maintain the right kind of energy while also driving towards a more formal, repeatable, standardized process? You definitely can't lose the adhock nature of things, because reality is that most ideas come from one person at some point,. And the way those get socialized is in an adhock way. On the other hand, if the structured meeting doesn't have the right people at the right time, like, it gets really hard to make rational decisions.