First of all, relax. No matter how you feel inside, this is not the do-or-die moment of your career. Remember that the editor wants to like your book. All you have to do is describe your story in words that will let her know what it's truly about. I can't find my own high concept with both hands in the dark. But I can talk succinctly about story because of Debra Dixon's wonderful explanation of goal, motivation, and conflict. Because of her, I can offer
Say a few words about the publisher or agent that suggests you’ve done your homework, read their authors’ work.
I’ve written a word count, subgenre
set in location and/or time period.
My Title is about a character tag (descriptive adjective and specific noun)
Fighting/striving/struggling for character goal
because character motivation
But conflict (why can’t she have what she wants?)
The other primary character (hero or heroine)
is a character tag
who wants character goal
so that character motivation
A sentence about how the romance is affected by or impacts the plot.
A sentence about how the characters work together or at cross purposes to defeat the antagonist or overcome the conflict.
A sentence establishing your area of expertise or level of excitement about this story.
Finish by telling her what you want: “I would like to send you the story.”
Have a second pitch prepared in case the editor says this project doesn’t meet the needs of her house at this time or asks what else you are writing.
That's it! Good luck.
Before any appointment, of course, you want to do your research. Make sure you have already visited
Agent Query - An excellent guide to what an agent is and how to submit to one,
along with a free, searchable database of over 700 agents.
as well as Preditors and Editors
Another Realm hosts this guide to literary agents and publishing houses.