11/06/2013
Because a couple of people have asked: although the terms copyediting and proofreading tend to be used interchangeably, they really are different processes. Proofreading is reading against a proof copy. A proof copy is a final typeset product ready to go to the printer. In the old days proofreading was done on a paper copy of the book. Now all the proofreading I've done has been on a pdf. The proofreader reads the proof against the author's manuscript to make sure the two copies match up (pages aren't out of order) and to catch typos.
Copyediting is done in earlier stages of the book. The copyeditor checks a doc file in Word for mistakes and makes corrections, usually tracking changes, on the doc before the manuscript is converted to proof form. Copyediting can be as light as just checking for misspellings and typos or can be more involved with suggested word changes, and grammar checks as well as misspellings and typos. Editing is a different skill and there are several different levels of editing. (But that's a different post.)
Generally, when I proofread, I try to get a second reader, one of us reading the manuscript and the other the proof but I can proof using two screens. When I'm copyediting, I run the doc first through spell check on Word, and, if I'm doing a deeper copyedit, through PerfectIt (a Word Add-on program), making notes on the side (on a piece of paper) of things I want to recheck. Then I begin "eyeballing it" - that is reading for things the programs miss. Most material gets read twice.
If these sound like skills you want to develop, I suggest you start with the Editorial Freelancers Association: http://www.the-efa.org/
PS Facebook thinks copyedit as one word is wrong, but it's correct although the spellings copy edit and copy-edit are also correct. This is why you need to learn the rules and not depend on grammar and spell checks.