Question of the day: I've spent months on revisions. In addition to querying new agents, I would like retry some who rejected. How is the best way to approach this?
Tricky question, and I'm not sure that there is a perfect solution here. To begin with, I wouldn't requery anyone whom you've queried within the past six months. Overhauling a manuscript (especially your first) takes time, and I don't think agents would think you've done a fair job (and aren't thus wasting their time) if you'd managed to do this in a few months or so. From there, I'd start off by personalizing your query to those who gave you positive feedback the last time. Something along the lines of,
"Dear XX, Back in June of '09, I queried you with TITLE OF BOOK. At the time, you thought I needed to sharpen the conflict and dialogue. I have spent the past year doing just that, and I'd welcome the opportunity to requery you."
And then I'd post your query. The above language is rough and just off the top of my head, but you get the idea.
I'm inclined to say that if someone just flat-out rejected you, I'd let it go. Unless you've overhauled the CONCEPT of the book, not just the writing. Don't forget that when an agent reads a query letter, he or she isn't reading your ms - she's just reading the general synopsis, and if she thinks a book isn't for her six months ago, she likely won't believe it's for her now. Of course, this isn't always true, and if in your heart of hearts, you think that Agent X will fall in love with it and may have overlooked it in her slush pile, I suppose it doesn't hurt to retry. (But I would do so with very few agents.) As for those you never heard back from? Well, I'd just query them as if it's your first time. They may not have really read your query very closely, and I doubt that it will be remembered such that they'll find you annoying or pushy.
But again, I'd proceed cautiously. I don't think it's the end of the world if an agent remembers your initial query (and the rejection of said initial query), since you can say that you've overhauled the book if asked, but still, you don't want to waste an agent's time, and have her remember you permanently as a pain in the ass.
Just my opinion. Anyone ever done this? How would you advise this reader to proceed?