The art of sleeping in seminars

1. Always lean forward, not backward. If you lean backward, your mouth will fall open and you'll snore.
2. Never sit back against a wall. Your head will bang against it, waking the rest of the audience. (Similar remarks apply to desks.)
3. Never sit on a couch. People won't like you sleeping on their shoulders. Also, couches are against walls (see 2.). An important exception is when you are alone on the couch, in which case it is preferable to a chair. In that case you can avoid 2. by leaning to the side.
4. Don't bring pencil and paper. They make too much noise dropping on the floor. You might think you can work during the seminar, but you just wake up with half-written equations with long angular lines at the end. Erasers are OK.
5. If possible, choose a chair with padding. Plastic and metal chairs also fall noisely.
6. Don't bother wearing sunglasses, or asking questions right after you wake up. Who do you think you're fooling?
7. If you wake up to laughter and everybody is staring at you, probably the speaker just referred to your work, so take it as a compliment.
8. Practice waking up to the sound of silence. That way you can wake up to the quiet just after the speaker finishes, and avoid being wakened by the irritating sound of applause. For you deep sleepers, this also avoids the problem of waking up in an empty seminar room. Don't think using watch alarms is clever: After the first 30 seconds of the alarm everybody will know anyway.
9. Don't get too much sleep the night before a seminar. You'll fall asleep in the seminar anyway, and when you wake up you'll feel sluggish from getting too much sleep. For the same reason, don't attend too many seminars in one week.
10. If you travel, be careful not to attend the same seminar twice. You'll sleep through the same parts anyway.
11. Older physicists tend to sleep at exactly the same time every seminar. Try to schedule your nap to not coincide. The speaker should always have at least one listener awake at all times, especially when he finishes. Nothing is more embarrassing than to wake up in a full room with no speaker.
12. Don't read this paper during a seminar. It will keep you awake, but the people sitting next to you will want to borrow it and you'll never see it again.

Retirado daqui.