Consider this sobering fact: if you spend, say, five hours a week in meetings that are boring or irrelevant, that's roughly six full work weeks each year that you're wasting and will never get back.
Obviously, it's in your best interest to attend only those meetings that are relevant to what YOU want to accomplish. Unfortunately, your coworkers (and bosses, alas) might not see it that way.
Many people believe that "communication" has value in and of itself, rather than just as a means to an end. They therefore hold meetings in the wrongheaded belief that talking is the same as working. (Hint: it's not.)
There are also executives in this world who use meetings as a way to establish authority. For these idiots, nothing says "I'm the boss" better than forcing everybody to sit in the same room for a couple of hours.
Anyway, since you can't avoid every dumb meeting, it's in your interest to learn how to extract yourself gracefully from the dumb meetings you can't avoid. Here's how:
1. Have a compelling excuse.
As much as you'd like to say "I'm leaving early because I know this is going to be a snooze-fest," you'll need to come up with a reasonable excuse for leaving early.
Match the seriousness of the excuse to the clout of the meeting leader. If a peer calls the meeting, then "I've got another appointment" is excuse enough. If your boss's boss's boss called the meeting, then the excuse should be something like "I'm having brain surgery."
2. Arrive early.
When you arrive early, you can claim a seat near the door (see #3 below) and have time for a quick chat with the meeting leader (see #4 below) before the other attendees arrive.
In addition, arriving early communicates to the team leader that you think their meeting is important, even if you privately believe it's a load of bollocks. Leaving that impression smooths the way for you to leave without ruffling the meeting leader's feathers.
3. Sit near the door.
4. Inform the meeting leader.
I read a couple of recommendation that you should warn the meeting leader by email before the meeting that you'll be leaving early.
I'm not sure I agree.
If you forewarn the meeting leader, you might get pushback. However, if you wait until just before the meeting starts, on the other hand, the meeting leader doesn't have time to argue with you or question your priorities. Plus they'll be thinking about getting the meeting started.
5. Leave yourself wriggle room.
When you tell the meeting leader you'll be leaving early, keep the exact you're going to time to yourself, because that leaves you with the maximum flexibility. Heck, you may be able to duck out fifteen minutes after it starts. (Hooray!)
However, if the meeting leader wants to know exactly when you plan to leave, provide a time that's at least 10 to 15 minutes earlier than when you actually need to leave.
When you longer than the time you claimed that you need to leave, it implies that you respect the meeting leader so much that you were were willing to be late to your other appointment.
Also, leaving yourself some wiggle room gives you a better opportunity to leave during the most convenient break. (See #8).
6. Recruit a note-taker.
Just before the meeting starts, turn to somebody who's sitting close to you--preferably somebody with less clout than you--and ask, loud enough for others to hear: "I have to leave early... can you take notes after I've left?"
This locks down the impression that you believe the meeting is important (even though you think it's not). Such a statement also gives your coworkers notice that, when you disappear, it wasn't because you were bored. (Even if you were.)
7. Don't spread out.
Since you're gonna want to make a quick exit, don't lay out all your stuff. Keep everything in a neat pile so that--ZIP!--you can leave a moment's notice.
8. Wait for the break.
The best time to slip away is when everyone's on a bio-break.
However, if you're unfortunate enough to work with people who have strong bladders, you can leave when there's a break in the action, like when there's a natural pause in the presentation.
I personally tended to make my escapes when somebody of lower status than me asked a question, since that implies that while I care about the meeting (which I didn't), I don't care about what that particular dude has to say (which I didn't.)
9 Give a "nod" then leave.
Since you've laid the groundwork and soothed the egos, all you need do to make your exit is to quickly gather your stuff (see #7), give the meeting leader a respectful "nod," and, woohoo!, you're free.