There is a post on the Reader Views blog with this same title, written by Sheri Hoyte, Managing Editor, and President Book by Book Publicity.  Ms Hoyte is also a reviewer.

Sheri Hoyte

This post caught my eye, because I’m a terrible proofreader.  In the course of writing a novel, I will re-read what I’ve written at least half a dozen times, yet once I send the manuscript to a copy editor, it will be returned with corrections on every other page.  Admittedly, some of these corrections are quite minor, and most would probably miss the attention of the average reader, there are still too many (mostly punctuation) corrections.

One thing that’s good for me about the copy editing process is that I’ve learned some of the finer rules of punctuation and grammar, which makes the editor’s job easier the next time.

Ms Hoyte says, “Proofreading is the most basic of all editing functions.  It can also be the most overlooked or neglected function in the process of getting your book published.  Taking the time to check your document for punctuation and spelling mistakes, and grammatical and formatting errors, can take your finished product from good to great.  Proofreading should not replace professional editing.  Rather, proofreading should be done before sending the manuscript to be edited.  The cleaner the manuscript, the better the chances the editor will catch everything else through their special lens.  More importantly, the cost of editing a well finished manuscript will be less than a messy one for sure!.”

She then offers these specific tips:

• Don’t depend on the spell checker and grammar checker built into your word processing program.  Spelling and grammar checkers are a great place to start, but they don’t catch everything and shouldn’t be considered the final word.
• Patience.  Proofreading is about as monotonous as it gets, but rest assured that it does get easier with practice.  Set yourself up for success by creating a distraction-free zone; put the phone away and turn off the music.  Steer clear of anything that may cause your concentration to stray.
• Don’t try to proofread something you’ve just spent hours writing.  Your brain and your eyes need a break.  It’s too easy to overlook errors when you are tired and have been working on the same thing for too long.
• Proofread from a hard copy.  Online writing software is great, and I love technology – almost always; but there is something to be said for spreading your document out on the table and getting down to business with your red pen.  It’s easier to gloss over errors on a screen that oftentimes jump out at you on paper.
• Read slowly and read everything.  Read every single word.  Slowly.  Again.  Get the picture? Oh, and don’t skim past the obvious places errors like to hide, such as chapter numbers and titles, page numbers, character names, addresses, capitalization, etc.
• Have someone else read your work.  Often a fresh set of eyes may be just what you need to put the finishing touches on your masterpiece.  

Ms Hoyte is right about the spell and grammar checker.  I have found that the grammar checking function is nowhere near sophisticated enough and that the spell checker can be wrong.  If I re-read slowly and carefully – every word – assuming that there are errors buried here, I find I do a better job.  If I re-read just after I’ve finished writing, I’ll catch the glaringly obvious mistakes; the less obvious ones get caught months after writing in a hard copy review.  There’s something foreign about the hard copy which makes me unconsciously suspicious of its content.  Then, there’s my wife, who’ll say, “Are sure this is right?” and “This isn’t working for me.”