"How To Tell A Story" by Mark Twain outlines the four most important basics to humorous American storytelling.
The first basic he mentions is "to string incongruities and absurdities together in a wandering and sometimes purposeless way, and seem innocently unaware that they are absurdities".
The second aspect of storytelling is "the slurring of the point".
The third funny tenet is "the dropping of a studied remark apparently without knowing it, as if one were thinking aloud".
The fourth, and most important basic for American storytelling is "The Pause".