I'm most interested in the project you're querying me about. I'm interested in what the book is about.
I am not interested in:
1. who edited it;
2. who read it before I did (not blurbs, not your teachers, particularly not other agents);
3. if it was in a contest or even did well in a contest unless it WON. This is the hardest part for authors to really believe, but it's true;
4. how long it took you to write;
5. what your job was or is unless it relates specifically to the book. (In other words, if you're writing science fiction you don't need to tell me you were an insurance adjuster before retiring to write full time);
6. how you found me. (Opinions vary on this subject) To me it seems rather obvious: you did find me. I want to read your query letter. Let's just chalk that up to the universe bringing us together and leave it at that;
7. Excuses or apologies of any kind including but not limited to
A. I know you're very busy and get a lot of query letters
B. I'm unpublished
8. Statements that you've followed the instructions. At this point, I know what I've asked for and I can tell if you've sent it.
Now, you can put all of that IN the query letter if you want. You can put anything in it you want in fact, but it will defeat the purpose of the letter.
I want to know about your book. You've got about 250 words to catch and hold my attention. Why would you waste it telling me ANYTHING I don't really need to know.
The only thing, let me emphasize the ONLY thing, I'm looking at is whether you can write well, and if I think this is a book I can sell. I don't care if you're a monkey from mars, and found me listed in the Agents Who Think They're All That and a Bag O'Chips list: write well, and tell me about a book I want to read.