For the record, I got my agent without an offer, but I had some short story sales, and I went through the Query-Manuscript Request-Get Rejected-Try Again With Another Novel process.
It looks like Black Art from the outside, but from the inside, it's just persistence, politeness, and writing as well as you possibly can.
Also, that trick with the oranges and the brass monkey doesn't hurt.
In other news, I could eat a cow. Maybe the malaise is shifting.