When editors ask for "clean copy," they are not reminding you to wash your hands before using your keyboard. Instead, this industry term refers to a manuscript that requires minimal editing before publication. In practical terms, this means error-free prose that follows editorial guidelines for the specific venue. The more work you put into cleaning up your copy, the less work editors will need to do and the more likely they are to buy your content.

Why Your Prose is Dirty

Even if you’re a neat freak, you may struggle to keep "dirt" out of your prose. Errors in style, format, grammar, and word choice are the "dirt" that prevents your copy from being "clean."

Three root causes underlie many common errors:

• Language is primarily oral. We think of words as they sound, not as they are spelled, and thus frequently confuse homonyms, words that sound alike but are spelled differently, e.g. "they're," "their," and "there."
• We read with our minds, not just our eyes. Fluent readers don't read words letter by letter, but instead use their knowledge of a language to recognize common words and phrases based on only a few letters. When you read the sentence "Proofreading improves teh quality of you're content," you may automatically correct "teh" to "the" and "you're to your" without consciously noticing the error.
• We see what we want to see. When we read our own writing, we know what we intend and often see through the writing to some ideal in our heads rather than paying close attention to the actual words.

De-familiarization

Good proofreading requires bad reading. To edit your work effectively, you need to unlearn the skills that allow you to read quickly and fluently, and revert back, temporarily, to a less sophisticated method of reading, in which you examine your copy word by word and even letter by letter.

Just as when you write about a location, even one where you may have lived for decades, you need to put yourself in the mind of someone visiting it for the first time, so you need to "de-familiarize" yourself with your work to proofread it, reading not from your own perspective but from that of a stranger approaching the manuscript for the first time.

Theory into Practice

Understanding how the nature of language contributes to making errors can help you create an effective editing workflow by following these four maxims:

• Procrastination is good. The Latin poet Horace recommended that you put away poems for nine years before publishing them. Although modern editors have far tighter deadlines, getting a full night's sleep before proofreading will increase your accuracy.
• Spell check is stupid. In a literal sense, spell checking software acts by brute force, looking for syntactic patterns and spelling errors rather than applying intelligence to understand meanings. Your spellchecker does not know the difference between a town notable for its "beers" and one frequented by "bears," but the difference is very important to most tourists. Avoid auto-correct and consider each word carefully when editing.
  Embrace habitual errors. Just like the French have their favorite cafes, so writers have habitual errors. Maintain a list of your habitual errors and search your work for them.
• Talk to yourself. As a native speaker of oral English, you learned the grapholect of written English as a second language. When you read aloud, your native speaker intuition catches errors you may miss while reading silently. If you are doing this at a coffee house, pretend to be talking into your phone to avoid worrying other customers.