Do you ever walk out of a meeting without knowing what comes next and who's in charge of handling it? If so, you've just wasted your time.
A meeting is an expensive proposition-- it monopolizes time for everyone involved. They disrupt the flow of an otherwise productive day. Calls and email go unanswered. If you're going to have a meeting, you need to do so for a reason with a specific outcome in mind.
To ensure that your meetings are worth the cost, you need to institute one simple habit: Never leave the meeting without asking: So what is the next action here?
This simple question will help you prevent a meeting ending without a clear, actionable direction to pursue. Raise the issues at hand with the people who absolutely must be there, and conclude with your "next action" question. When you've answered the "next action" question, you'll know what to expect and who to expect it from. Not only is this useful for your office meetings, but it can be invaluable to making sure client meetings are effective, too.
And yes, there are opportunities for less formal meetings... they're called lunch!