Go pick up a novel of a writer whose style you admire. Say it's Gabriel Garcia Marquez - he's about as unmarketing-speaky as you can get. Open to any page. Now copy the words of the page into your own notebook.
When you're finished, start writing what you need to say about your product. You'll find you're doing it in an entirely different voice.
You can do this with Hemmingway and Steinbeck as easily as you can with Dan Brown and David Sedaris. Go ahead and try some poetry. Works with Sandberg and Billy Collins, too.
Art directors: Do the same by taking out a big book on fine art. Or photography. Or design. You don't have to recreate each painting. But you can try. Sketch out the composition. Study the shadows and the colors. Spend a half hour with a particular style. Then jump into your layout while it's fresh in your brain.
Small trick. But it works. And it's much better than staring at a blank page, or just writing and laying out what you think the client (or the awards show juries) expect.