Elizabeth Lyon is great. She's down to earth, makes sense, doesn't condescent, tells it straight and seeks to be helpful, always. I met her at a writer's conference two years ago and agreed to let me interview her for a piece I was pitching. I've exchanged some emails with her, though not lately, and she always responds thoughtfully and thoroughly.
I've used her book and like it very much. I've used the other two main books (Jeff Herman's and Michael Larsen) and honestly, I think the trilogy works best because they each have strengths in giving you tips on how to put a nonfiction proposal together. I even emailed her a few times while I read the book to get clarification on how certain things might apply to my proposal.
I think she's worth reading, meeting and even emailing before you go to the conference, then she'll know the name and the face.
She has a website, but I forget the address. If you google her name in quotes, you should be able to find it.
Good luck! Where's the conference?