Science Fiction appeared as a complex, self-contained microcosm in the fourties, with first rate minds enlivening what was considered a low-brow form of diversion. How did writers like Heinlein and Asimov learn how to write science fiction? They way other writers learned to write literature: by doing it until they did it better then doing it more. Now you can attend classes that help you write better aliens.

The best aliens were always simply the reader of the story.