Matt Curran, of The Secret War fame, has posted a splendid essay on his storybuilding process on his blog.
Matt tends to be a start-with-an-image (or situation) kind of writer, and his images tend to be climactic ones, so he generally builds from the ending back to the start--but any summary I give here doesn't do justice to his description. (So go read it, already.)
The best news is that Matt has so much to say on the topic that he plans to post installments, of which this is only Part I.
I'll drop notes alerting readers to additional posts on the topic at his site--but remember that links to all the posts on this particular topic can be found by looking to the sidebar on the right under "Looking for These?" and clicking on WRITERS DESCRIBE THEIR STORYBUILDING PROCESS: Index.
PS to Matt: The Secret War finally arrived in my mailbox today.