All three are correct, but for the purposes of this discussion, we’re looking at in-house style guides that are used when you or a freelancer are writing things like case studies, white papers, manuals, ads, and other marketing collateral. Using an in-house style guide provides clear guidelines on which words to use, which words to avoid, and how to format your documents.
I’ve worked extensively with in-house style guides. For an apparel company, I helped create the grammar and branding portion of the style guide, using words that described the company, detailing words to avoid, and laying down guidelines for using the Oxford comma (you can guess how that ruling went.) When I copyedit for Copyediting, I check to make sure the copy is consistent with the in-house style guide, as well as Chicago style. And way back when I was a technology journalist and copy editor, I used to update the style guide for IDG News Service.
In each case, the style guide is invaluable in terms of keeping copy on track. Most style guides, especially for branding, will also include sections on graphic design and the use of graphics. The one I did for the apparel company also included information on using the trademark symbol, use of the tagline, and which style guide to defer to when writing different collateral. I also covered how to use the company name in marketing materials and the preferred spelling of words like email and website.
Whether the style guide is used in-house only or distributed to freelancers, it creates a unified front for communications coming from the company. For example, if you’re hiring a white paper writer, giving her a copy of the style guide lets her see how you want your company presented and gives her an idea of the grammar and spellings you prefer, like Web site vs. website. It also points her to the correct style guide to use for questions not covered in your in-house guide.
If you’re planning to produce a lot of content, contact me to learn how I can help your company put together a comprehensive style guide that will pay for itself in terms of consistency, clarity, and time saved.