I would like to write a short story, but I am daunted by the idea that something so short needs to have a beginning, a middle and an end and that the characters need to be believeable but are not given much time to establish their uniqueness.

I would like to write a short story that is satisfying, has something to say and is not a time-waste for the reader.

In short: how do you create a perfect nugget of fiction in a few thousand words?

Maybe the best advice is a good example. What is a classic short story that flowers within the constraints imposed upon it?