Ripped from the pages of Wikipedia:
In his book Bagombo Snuff Box: Uncollected Short Fiction, Vonnegut listed eight rules for writing a short story:
Use the time of a total stranger in such a way that he or she will not feel the time was wasted.
Give the reader at least one character he or she can root for.
Every character should want something, even if it is only a glass of water.
Every sentence must do one of two thingsâ€”reveal character or advance the action.
Start as close to the end as possible.
Be a Sadist. No matter how sweet and innocent your leading characters, make awful things happen to themâ€”in order that the reader may see what they are made of.
Write to please just one person. If you open a window and make love to the world, so to speak, your story will get pneumonia.
Give your readers as much information as possible as soon as possible. To hell with suspense. Readers should have such complete understanding of what is going on, where and why, that they could finish the story themselves, should cockroaches eat the last few pages.