Summarize this article:

Before you start the detailed work of copy editing, familiarize yourself with the content, tone, and formatting of the entire text. This will help satisfy your curiosity as to what the text is about, and will familiarize you with the author’s writing ability and style.  Make sure that you understand the goal or objective of the piece as well. If you’re editing a long text (say, over 30 pages), you may need to skim a chapter or section at a time. If you’re copy editing your own text, you can probably skip this step. Spelling errors crop up in every text, and it’s mostly up to copy editors to catch and correct them. Also, correct words that, while not misspelled, are incorrectly used. For example, if an author meant to write “thorough” but instead wrote “through,” change the incorrect word.  If you’re editing with a word processing software, it will catch many errors for you. Keep your eyes open for spelling mistakes still, though, since digital spell checkers aren’t perfect and can’t edit based on context. As you edit the copy, make sure that it follows correct grammar rules. Correct any ambiguous or incorrect grammar. While an author may perceive these edits as superficial, correct grammar is integral to the meaning and structure of good copy. If you’re unsure if a specific instance of grammar is correct or not, consult your style guide. Grammar errors that you should spot and correct include:   Subject-verb disagreement. Dangling or misplaced modifiers. Inconsistencies in verb tense. You’ll need to refer to a style guide or grammar manual, which explains correct punctuation usage and rules. Edit the text so that all punctuation adds to the clarity and readability of the copy. An important part of this step is to make sure that authors use commas correctly.  For example, an inexperienced author may place a period or comma outside of quotation marks. Fix any misused em- or en-dashes, or hyphens. Authors who are deeply entrenched in their fields often forget that lay readers will be unfamiliar with many common abbreviations and acronyms. This is especially prevalent in scientific or technical writing. Catch these missing definitions and insert them.  Acronyms should be defined at the first usage. For example, USGS should be defined as or “the U.S. Geological Survey.” Units of measure should also be define. For example, if you’re editing a paper on hydrology, “ppm” should be defined as “parts per million” when first used. Common measurements like “cm” may not need to be defined. Consult your style guide to find out.

Summary:
Skim the entire copy before you begin editing. Correct spelling mistakes and word usage. Correct grammar errors. Search for and fix any errors in punctuation. Make sure that all abbreviations are defined.