A few tricks that can catch meeting that a more or less guaranteed to be useless (in IT):
* Does it have less than 10 people attending?
* It there an here an agenda?
* Is there more technical people than managers?
* Do you know why you've been asked to attend?
If you can answer "No" to any of those questions, you're going to have a bad time. Now you can have meetings where you answer yes to all of the above, and it's still useless, but the chances are lower.
I think only the first and last are really important. I've had very effective meetings where I was the only technical person and we didn't have a formal agenda. Often meetings with stakeholders where I wanted to know what I could do for them; what they needed. So I guess that's still an agenda, but more important is that I was in control and the meeting was small.
Being a bystander in a big meeting, that is the worst. If it doesn't affect me and my input is not needed, why am I there?
only know to be useless after having had the meeting, and the decisions or discussion were either moot, already known, or completely expected.
So how do you know whether a meeting is required, before organizing and/or attending one?