The Gregg Reference Manual:
A Manual of Style, Grammar, Usage, and Formatting, 11th Edition
William A. Sabin, McGraw-Hill, 2011
The Gregg Reference Manual is intended for anyone who writes, edits, or prepares material for distribution or publication. For over fifty years this manual has been recognized as the best style manual for business professionals who want to master the on-the-job standards of business professionals.
FOR NEWSLETTERS AND BLOGS
The Associated Press Stylebook and Briefing on Media Law
Edited by Darrell Christian, Sally Jacobsen, and David Minthorn, Associated Press, 2010
The Associated Press Stylebook, first published in 1977, clarified the news organization's rules on grammar, spelling, punctuation, and usage. Now in its sixth edition, the Stylebook is the standard style guide for most U.S. newspapers, magazines, public relations, and consulting firms.
The Chicago Manual of Style, 16th Edition
The University of Chicago Press, 2010
“Chicago” is the bible of book publishers. We refer to “Chicago,” but it is a specialist’s volume. Unless you’re a professional editor or proofreader, this style guide is not needed by most business writers.
FOR EVOLVING LANGUAGE
Garner's Modern American Usage, 3rd Edition
Bryan A. Garner, Oxford University Press, 2009
I like this resource because it includes a "Language-Change Index," which indicates how well accepted a term is, ranging from Stage 1, widely considered incorrect, to Stage 5, universally accepted as correct. Because business writing language is ever-evolving, this is a helpful guidebook to determine if a usage is now acceptable.
FOR UK AND US ENGLISH STYLE DIFFERENCES
The Economist Style Guide, 2011 Edition
This guide contains a very helpful section on American and British English.
American and British business writing is essentially identical. There are spelling and minor punctuation differences, that this text illustrates perfectly. By the way, you should construct documents in your style. If you are British and writing to an American, for example, use British English, rather than American English. Do not use idiomatic expressions or vague phrasings, of course. There is never any significant misunderstanding between UK and US English, as long as one avoids idiom and writes clearly. Trying to adopt a style and voice that is not your own rings false.
INTERNAL STYLE GUIDE
Do you wish to compile style guidelines, unique to your organization? For example, you may have specific terms you want used with consistency in all documents. Many organization compile an internal style guide, and share it with all employees.
Many thanks to the ASTD LinkedIn group for sharing a generic internal style guide, which you can use as a model. (Yet, another reason you should join LinkedIn if you have not yet done so!)
Download a copy of this Business Writing Style Guide Internal Template.