Sue has pointed writers to a good post about preparing your manuscript for editing using spell check.
Even though I am an editor, I am a writer too, so I want people to save a little money if they can and prepare their manuscript for editing.
But besides spell check (which frequently happens automatically as you type), I recommend to my clients that at least 2 other people read their ms before they have it professionally edited. It also helps if you ask your readers to look for grammar and punctuation errors, beside the other things you need help with.
Most people know the basics, and they can save the editor time (and thus your money) if they catch some of the simpler things for you. Happy writing!
Why, you ask, would an editor give advice on how to save you money on her services? Won’t that make less money for her, you ask? In the short term, yes. But looking at the bigger picture, you’ll get a better editing job if I don’t have to worry as much about the small stuff. Therefore, I would love it if you’d read and take to heart this article on running spell check before submitting your work for editing. Thanks to libroediting.com for their wise words.