"Hold the reader's attention. (This is likely to work better if you can hold your own.) But you don't know who the reader is, so it's like shooting fish with a slingshot in the dark. What fascinates A will bore the pants off B."
from Margaret Atwood (who of course I have never read, since I have never read anything, especially if it's fiction, which I suspect is what she writes)
also from c.t's blog , which includes 9 other, less important, but still entertaining rules.