I'm trying a script consultant this month for the first time ever. I'll let you know how the experience goes, but in the meantime, here is an article (written by the service I'm trying -- Script A Wish) outlining some reasons why you might want to consider using a reputable script consultant as well.
3 Tips for Getting Your Script to the Studio Level
Here's another great article from Michael Ferris.
Writing a Killer Query Letter
Michael Ferris, a writer for ScriptMag.com and an industry vet, recently posted this article on writing a query letter that will get your script into the right hands. The article also has a few things to say about who to send your query to and tips on writing a great logline.