Back in my memorable school days, I had to attend quite a few unmemorable events, including seminars, skill building workshops, public counselling sessions, mandatory cultural programmes etc. The reason I don't remember half of them is that I drifted through those events sleeping with my eyes open, or was busy passing comments and laughing with friends. Now that I've grown up, or I think I have anyway, I wish I had not done that, because it is extremely rude, and also because I missed out on a lot for not being attentive. Honestly, I realised this when I was on the other side of the microphone at a recent event in my university. And from my cumulative experience, I have formed a few observations.
Don't be late. Your late entrance will divert attention of the audience off the speaker, thus making it difficult for the session to continue. Moreover, don't ask questions unless you are absolutely sure those haven't been discussed prior to your arrival, as it annoys others and hinders the progression.
Make sure that your phones are switched off or in silent/vibration mode. Needless to say, your ringing phone annoys the daylight off others who are actually trying to listen, and in fact causes disruption.
Don't talk over the phone. Unless absolutely necessary. Even then, please lower your voice. I have been at a workshop where someone was talking over the phone, and was very loud. To this day I remember what she instructed her servants to prepare for dinner, but hey, I'm not telling you about the shutki bhorta. What I mean is that it's very annoying.
Don't talk amongst yourselves while in the audience. At a recent such conference I attended, an esteemed intellectual had to boldly ask the audience to remain quiet as he was feeling aggravated. The worst part, he had to pause his speech to deliver that message. It is very insulting for a speaker when you talk in the audience, that too, loudly.
Don't interrupt the speaker. Firstly, it hampers the steady flow of the session. Secondly, it is in bad taste to interrupt someone while they are speaking. If you have any question or opinion, keep it to yourself till the floor is open for questions or comments.
Respect others' opinions. Often, people tend to impose their opinions onto others, especially in the form of questions. It's one thing to have a contradictory view that you can express, but it's different to boldly tell the speakers of the conference that their opinions are wrong. It's simply a no-no, and you should respect theirs if you want them to respect yours.
Don't sleep during the conference/workshop. Just don't. If you are extremely drowsy, excuse yourself and go wash your face, or just go home and sleep. But do not sleep when the workshop/seminar is going on. It is a very, and I mean VERY, insulting gesture towards the speaker.
Workshops and seminars are meant to be forums for discussion and sharing of knowledge. The speakers are often those who have some experience in the fields being highlighted, and it's your chance to learn from them. Therefore, maintain a healthy learning atmosphere, and learn.