A joke should have the perfection of a haiku. Not one extra word. No wrong words. It should seem to have been discovered in its absolute form rather than created. The weight of the meaning should be at the end. The earlier words should prepare for the shift of the meaning. The ending must have absolute finality. It should present a world view only revealed at the last moment. Like knife-throwing, joke-telling should never be practiced except by experts.
For many laymen, a joke is a heavenly gift allowing them to monopolize your attention although they lack all ability as an entertainer. You can tell this because they start off grinning and grin the whole way through. They're so pleased with themselves. Their grins are telling you they're funny and their joke is funny. The expert knows not to betray the slightest emotion. The expert is reciting a fact. There is nothing to be done about it. The fact insists on a world that is different than you thought. The fact is surprising and ironic. It is also surprising--you mustn't see it coming. That's why the teller should not grin. His face shouldn't tell you it's coming. If the joke is also vulgar, so much the better, but it must never exist for the sake of vulgarity. That's why "The Aristocrats" is not only the most offensive joke in the world, but also, in the wrong hands, the most boring.