Lessons from Nancy Kress.

--The first sentence is important: you shouldn't just have a "hook" to the sentence, you should promise conflict or change in the first sentence.

--The first three paragraphs in a short story, the first three pages in a novel: that's how long you have to grab an editor's attention.

--The first three paragraphs (or pages, for a novel) should include character, development of the conflict or change promised in the first
sentence, specific details that make the situation/setting believable.

More later, unless I don't learn anything else.