It won't help the OP now, but I once saw this advice in a How-To-Write book (I forget which one)--start by writing a
one-sentence summary of your book. Such as
"Luke Skywalker leaves his home planet, teams up with other rebels, and tries to save Princess Leia from the evil clutches of Darth Vader."
or
"Rescued from the outrageous neglect of his aunt and uncle, a young boy with a great destiny proves his worth while attending Hogwarts School of Witchcraft and Wizardry."
(IMDB is a good source of examples for this.)
Next, expand the sentence to a paragraph. Finally, expand the paragraph to a few pages. Save all three versions.
This particular book advocated doing this as planning before you begin to write, which sounds quite horrific to me. I suppose it might work for some people. What does seem reasonable is the idea of doing it at the end of the first draft, before beginning revision. (Which is not to say that I've actually accomplished this yet.
)
For one thing, stopping to think about the big picture should give focus to your revisions. For another, you now have a query hook, an elevator pitch, and a synopsis. Or at least some raw material you can tweak to get those.
