When you’ve found someone who seems like a decent candidate so far, make first contact. (The contact form on the website is fine as a first step.) Introduce yourself and state what you are looking for (a developmental critique, copyediting, etc.). Give a very brief description of your project, including its genre and approximate length. Give an idea of your planned next step and any deadlines (even if only approximate ones). For example, have you already signed a contract with a subsidy press for publication next fall? Are you planning to submit the manuscript to publishers and/or literary agents after editing?
I usually ask for a 10-20 page sample – one page is a bit scant for a really accurate estimate. I’ll do an editing sample, too, but how long I’m willing to make it depends on the proposed length of the piece I’ll be editing. As for the “hidden message” strategy, if I saw something like that, I’d suspect the prospective client was fearful and suspicious and I’d probably run the other way. I willingly provide testimonials, references, and links to published work, so tricks aren’t necessary. It’s important to me to build a professional relationship of mutual trust with my clients, backed up, of course, by a contract that protects us both. I don’t think I’d like to work with a client who plays “gotcha!” Lots of good suggestions in this article, though.
It’s always sensible to follow due diligence in submitting your first draft of your book to an editor by making as fool-proof a copy as possible for you because first, it is your own creation, and secondly, a horrid draft sent your editor can end up frustrating both you and him or her. Make your own corrections to the extent you can, so that will make the job of your editor that much lighter and the end result would be a lot more effective.