Dear Agent Amazing:
I was wondering if you could read this query and give me some pointers.
This is for a second book I've written and I'm having trouble getting agents interested. This sample query you're about to read is the fifth or sixth re-write I've done. My book has a lot of twists and turns and I'm having difficulty explaining it in one page or less. Thank you for your time and patience.
--(redacted but not unknown!)
Don't write to an agent asking for pointers on a query letter.
If you need help with your query letter there is a place get that. It's called a writer's conference. Go to one. Go to several.
If you don't want to go to a writer's conference, get a book on writing query letters. Then read the damn thing.
This is the the kind of letter that makes agents look like Yertle the Turtle before he was King of the Pond: withdrawn, moody, bitter, and snappish.