First, humour must look effortless. Comedy must appear to happen by accident or the reader will feel manipulated.
Surprise is important to a good laugh. The unexpected often makes us laugh even when the situation isn’t funny.
As pleasant as it is to be silly in real life, silly doesn’t work on the page. It just looks stupid. A waste of reading time.
Then there's comic timing, a rhythm that's even harder to do in writing than in stand-up comedy. Short sentences are funnier than long ones and several short sentences together can be funny. Punctuation and spacing on the page can also contribute to comedic timing. A full stop is often funnier than an ellipsis or a comma.
Stand-up comics claim there are funny words. THIRTY-TWO is apparently side-splitting, as are: PUCK, KUMQUAT, PANTS, NOODLE and BELGIAN, among others. It must be the context or the human voice that makes them funny.
And good comedy is usually simple. Pared down. Succinct. A word tincture. Very difficult to do. Think Tolstoy's "Drops dripped", only funny.
Every time I sit down to write something funny, I break out in a sweat, my neck stiffens, my claws clench on the keyboard and I begin to cry. I’d never be able to earn my living as a comedy writer.
Not to worry, with the advent of the iPad, I'm pretty sure that e-books will soon have all sorts of audio and video links, including laugh tracks. We won't have to suffer so much as we write comedy, we'll just insert a link and slink away knowing that, even though we got a laugh, we failed to rise to the challenge of making readers laugh with mere words.