By the time a writer has polished the manuscript, he's lived inside the story so long he's lost objectivity. It's time for someone with fresh eyes. An editor will examine your work from a production perspective, but it saves a lot of time if you've first identified and fixed your story's weaknesses. That's where beta readers can help.
To paraphrase Wikipedia's definition, a beta reader is a person who reads a novel manuscript with a critical eye. A beta reader may highlight plot holes or problems with continuity, characterization or believability; and assist the author with fact-checking.
Many writers request fellow writers to be beta readers. I chose readers who weren't writers because I wanted the customer's reaction. I focused on readers interested in elements present in my novel, such as paranormal romance, the Gullah culture, or ballet. A few curious friends volunteered. I emailed nine potential beta readers. Here's an excerpt:
I'm contacting you because your interests and experiences give you the unique view I'm looking for in a beta reader for The Bad Death. Essentially, The Bad Death is a vampire slayer novel with a Gullah heroine and is slated for publication in summer/fall 2013. The details below give the cover art and synopsis; an explanation of a beta reader's contribution; my novel's characteristics such as length and similarity to its genre sisters; and particulars of the beta-reading period. I also attached the first few chapters. If you say "yes", I'll contact you again May 1.I made a similar appeal on a Goodreads discussion thread, with the moderator's blessing.
In addition to my heartfelt gratitude, I gave each beta reader an autographed copy of the published version, in the format of her choice.