How do editors choose stories?

Jeremy L C Jones interviews 10 editors of fiction, mostly magazine editors, for Clarkesworld, #33 (June 2009) on what makes them select a story from slushpile. A few responses that caught my eye:

1. Nielsen Hayden: "I'm looking for the thing I didn't know I was looking for."
2. O'Neill: "there's a very real hunger for the familiar among readers".
3. Schmidt: It's very unlikely that Analog will buy a story longer than 20,000 words.
4. Sizemore: 'A good "fit" for Apex are stories that show the reader the dangers of technology to the human condition.'
   
   Hmmm... doesn't sound like my kind of stories.
5. Nielsen Hayden: "editors aren't in the business of adjudicating what's good; we're in the business of acquiring and publishing material through particular channels and organizations, mustering the opportunities that actually exist."