This article is from the The Complete Guide To Hack Stand-Up Comedy, by Steven Rosenthal and Steve Silberberg (stevebo@onramp.net) with numerous contributions by others.
A typical trick is to pick someone up front to turn the audience against by
making the person look really stupid, either by pointing out their
confusion or by explaining the last joke to them. I know of at least two
comics who pick fun of the same seat at exactly the same time during their
acts.
THE HACK'S HANDBOOK also recommends asking the person their name and then
repeating the question in sign language as if the person was deaf. If you
truly have an idiot bothering you (not an uncommon experience) and you have
an interesting way to point out such stupidity, then by all means do it.
But don't slam somebody for the sole purpose of making you look smarter and
don't just make fun of their speech.
 
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