It does not pay a prophet to be too specific.

The story of civilization is, in a sense, the story of engineering - that long and arduous struggle to make the forces of nature work for man's good.

There is no mistaking the dismay on the face of a writer who has just heard that his brain child is a deformed idiot.

In writing a series of stories about the same characters, plan the whole series in advance in some detail, to avoid contradictions and inconsistencies.