Boredom...

Sat through a lecture by a Taiwanese architect trying to speak in English. Thought i was in some deep shit when he warned 'it might go on for 2-3 hours'. The shit was deeper. 2 hours of some god forsaken work he was shoeing while people were very happily leavin the hall. By the end, there were like 25 people, down from 150 at the start. Those 25 were busy messaging, gaming, chatting, podding etc. Which makes me think. What is the correct way to show boredom without offending someone. Especially someone who you have invited (like in this case). Tough q. i am kinda concerned about offending people especially those i don't know well or those i like. But can't say these people are the most interesting speakers. Or sometimes the party last night doesnt let me stay up (sorry Amita ma'am). Walking off is not an option. And a lot of times i can't even play on my cell. Or listen to the radio. My concern for insulting the speaker doesnt lemme crack jokes with a clean conscience. So what do i do? Have tried sleeping in various positions to be unnoticeable. And got caught every time the lights were on. Now my question for ANYONE who reads this is how do i get away with falling asleep???