I ask two questions at the beginning of most meetings in a very friendly and non-attitude way:

(1) "Hey, so whats the agenda here? What is it we all need to know by the time this is over?"

(2) "I have a conflict with another meeting. What do you need to know from me right now? (or what do I need to know from everyone right now?)"

Works wonders and also helps other people get to the point too.

In my particular case I don't turn up at most meetings. On rare occasions I'll get a phone call at my desk or someone will swing by, in which case I'll happily go.