From Some Rules of Writing by Nicola Griffith (one of a fairly extensive bunch of pieces over at the Online Writing Workshop, about which I know very little):
One of the clearest markers of bad writing is, in my opinion, the unexamined cliché. Think hard about every single word and phrase you use. Don’t write "her heart stopped" unless you mean she died. Don’t talk about saucy serving wenches in an inn where the beef stew is thick and hearty and the ale is fresh, nutty, and strong…unless you intend to use such a cliche to good effect, to twist it upon itself and the reader for a purpose. (Why aren’t "serving wenches" ever tired, middle-aged women? Why, in worlds with no refrigeration, is the meat never spoilt–or intensely flavored with spices to prevent/slow down said spoilage? Why is the beer rarely yellow, or thin, or cloudy with sediment? Why do barbarians always "come down from the north"? Why do people who fall over the edge of cliffs always "scrabble for purchase?") Stereotypes such as sly Arabs, money-lending Jews, feisty old women, dignified and wise kings, comic-relief peasants, green-eyed and raven- tressed heroines with "mouths just a bit too wide for beauty" and pert noses are signs of lazy writing and/or a failure of imagination. Many clichés are "self-evident truths": women are weaker than men; Americans are superior to Africans; humans are more innovative than aliens; women-only worlds would be boring, homogeneous places where the inhabitants sit around all day and think about men; capitalism is fabulous; all cultures appreciate art; genius is more valuable than compassion; straight men are more butch than gay men; Christians are more reasonable than Moslems; war is inevitable. The list is endless (or at least very, very long). All writers commit cliché to some extent, but the better you are, the less often you’ll do it. Clichés undermine fiction; they’re like rust on the cables suspending the reader’s disbelief. One is a little unsightly, but many mean that disbelief will come crashing down, your books or story will be tossed aside, and you will have lost a reader forever.