For the copy editor, the style guide is indispensable to superior and proficient editing. Without it, you might find yourself in a Mexican standoff with an author over the correct use of an em dash.
A style guide puts everyone involved in the creative process on the same page (Really? I just wrote a pun) when it comes to precarious subjects of preferred spelling, syntax, grammar, punctuation, capitalization, abbreviations, et cetera.
While it's always easier when the organization or publisher you are working with has already chosen a style guide, or has an in-house style guide of their own, experience tells me that, copy editors are sometimes on their own to ascertain the correct style guide to follow.
I use the following style guides:
- The Chicago Manual of Style, 15th and 16th eds.
- The Associated Press Stylebook (AP)
- Publication Manual of the American Psychological Association, 6th ed. (APA)
- The Elements of Style
- Franklin Covey Style Guide for Business and Technical Communication
- American Medical Association Style Guide, 9th ed. (AMA)
My list is not meant to be exhaustive—I am open to all style guides. If I missed your favorite, let me know in a comment below.