15 years ago they called me the shotgun query/submission king. Well it worked then, with those cookie cutter letters of intro, but it doesn't anymore. Six months ago I thought James Richie here, was off his lid about this quality isssue--he's not. It is all about being attentive, specific, and knowing your target agent/editor inside outside and backwards until you feel that you've slept with them and you know if they leave the toilet seat up or down and what kind of toothpaste they use.
Read and devour their websites--try to understand what their philosophy and mission statement is. Remember to comment on it, honestly, no pandering--give them the straight dope on how you think you can contribute to their roster with your fresh and innovative ideas and talent. If possible, read some of their author's books, throw in a few comments about how you found their themes and storylines, and what direction they took that pleased you. Name a specific book of theirs (that they repped) and how it comes close to your style and technique. Dig up a little history on their titles and spit a few stats at them, that will raise an eyebrow, believe me! Note that one of their authors was doing a signing in or near your home town and that you might like to check them out. Take note of one of their author's editors and don't be afraid to name drop............the point to all this is:
Personalize--personalize--personalize.
Show this agent, or even editor, that you've stripped away that magic veil and you know who is behind that curtain. This type of attention will garner nothing but respect and admiration from an agent/editor, who gets the same old blah, blah, blah, every day, day in, day out.
This, will put you at the top of the stack.
As for mulitple queries--I do them--but they are tailored now to fit the individual, and it's living flesh behind that desk that is tearing your letter open, or real live eyes reading that pitch on the screen. The idea is to snap those eyes open, and make them draw a surprized breath. Now how does this writer know that I attended so and so con in Break Neck Arizona, and that I like a little romance in my sci-fi? He's even a little opinionated about characterization, even a little snippy, but I like that aggresiveness. I'm intrigued--I want to know more about this person, who certainly knows a lot about me. We'll give him a shot.
Good luck and good hunting
Triceratops