Have you read Natalie Babbitt's The Search for Delicious? The King is writing a dictionary and wants to define the word delicious. For some that's an apple, for others it's...well, you get the idea. I've come to the conclusion the same is true for that elusive creature, the query letter. Personally, I couldn't bag it with an elephant gun. But, I did find an excellent group of articles done on Absolute Write that covers all/most/some of the possible alternatives and preferences.