Every company needs a style guide. And everyone employed by the company needs to know about it.
As the name implies, a style guide is a compendium of rules for language usage at a particular organization. It can (and should) include everything from the correct spelling of the company name to guidelines for appropriate descriptions of minority group members.
I’ve worked at publications that create their own guides from scratch, sometimes running 200 pages or more. But most places do just fine with an existing style guide supplemented by a list of exceptions and words specific to the organization.
In the United States, the most popular guides are the Associated Press Stylebook, favored by journalists and other language-forward types, and the more traditional Chicago Manual of Style. If you write for an international audience, check out The Economist Style Book, which offers a handy section on Americanisms and has the added advantage of being free.
Whichever guide you choose, your company should have a frequently updated, regularly circulated list of addenda to make sure all employees—especially those responsible for external communications—are on the same page. I’ve been called in to compile these lists, often after some publicly embarrassing incident, and I can tell you that employees desperately need them.