What I do is close my eyes and try to visualize the story as a whole, the main pieces, and see what that reminds me of. I can babble all day and try to explain the key elements of a story in ten words or less, and nothing original I write will come close to, say, "The twists of THE CRYING GAME but with lasers." So using pop culture references to established media properties can quickly communicate the style and feel of a novel.
Then I write four or five blurbs, and send them all to the publisher and let them decide. Sometimes they tweak it, as in, "hey, can we combine #2 and #4?" The answer is usually "yes," because they are still my observations about the book.