Consistent standards and clear communication in your brand's copywriting are very important. Potential customers don't like to shop in sloppy stores, and they won't like to buy from online brands that use varying standards of grammar. Essentially, your marketing department won't look like it has any clue what it's doing. By adhering to a single grammatical style, your marketing will look infinitely more professional.

The Big Three: Style Guides

MLA style is primarily academic. Many students have used this grammatical style before and, hopefully, they have a relatively good grasp on grammar because of it. Not the most thorough style guide, but it gets the job done. Any employee's passing familiarity with this is a good sign.
AP style is used primarily by journalists, but it's seeped its way into office work, internal communications, and students not in arts or sciences degree programs. This style guide is written primarily with the newswire in mind and plays it loose with punctuation in order to save on ink is mass-produced newspapers. Obviously, that's not a problem anymore with the advent of the internet.
The Chicago Manual of Style is a thousand-page tome that covers absolutely everything you will ever need to know about grammar, as well as everything anybody anywhere will ever need to know. You will probably only ever used a few chapters in this book. It's goal is to facilitate clear writing that leaves no room for misinterpretation. As a marketer, that should align with your brand's messaging goals.

Three Reasons to Use Chicago Style

Narrowing over a thousand pages of reasons down to just three is a daunting task. But here are the top three reasons copywriters should use The Chicago Manual of Style.

The Oxford Comma - Yes, this is a requirement for your marketing. This refers to the comma placed immediately before the last conjunction in a list of things (i.e.: Something, something, and something). With this seemingly-inocuous added comma, you can save readers from embarrassing miscommunications. Just read this tweet from Sky News: "Top stories: World leaders at Mandela tribute, Obama-Castro handshake and same-sex marriage date set." Now that would be a top news story! Too bad it's not the one they were trying to report.
Learn How to Hyphenate Adjectives - Compound adjectives get hyphenated to visually show that these two separate words are connected. That way, your reader won't have to backtrack over a sentence and read it a second time to figure out where one idea ends and another begins. This is why "My 3-year-old daughter" and "My daughter who is 3 years old" are both correct.
Subscribe Online - The Chicago Manual of Style is a department manager's dream. You can subscribe online for the whole department to reference and cite to each other! Or maybe that's just my dream. But having a whole department running with the same standards? That doesn't have to be the stuff of fairy tales.

Deep Dish Wisdom

I'm a huge advocate for the concise copywriting that can be done with The Chicago Manual of Style. So much so, that I'm going to really stretch this metaphor to make it work. Chicago-style grammar (much like their deep dish pizza) looks good to the consumer, has layers of goodness under the delicious toppings that people care about, and is now famous around the world for its quality.

I'll post more tips straight from this delectable style guide over time (and after lunch). Want to know more in a hurry? Get a free consultation for your business to see how unified grammar can help you look more appetizing to consumers.