I remember it like it was yesterday. I was checking out the list of required texts for my class COM 215: Writing for Print. At the top of the list in boldface and all-caps was AP STYLE GUIDE (NEWEST EDITION PREFERRED). I found a cheap copy on Amazon (because I am a savvy consumer), little knowing how useful that book would be over the next 6 years and beyond. Through school, internships, my professional life and even in my personal writing life, my AP Style Guide has been the Robin to my Batman; the Garth to my Wayne; the Scully to my Mulder. I’ve thought more than once about going to sleep with my AP Style Guide under my pillow so I could absorb its sweet, sweet knowledge via osmosis.

If you’re going to be writing your own content for your marketing efforts, correct style is hugely important. The smallest, most innocuous error, from using a word incorrectly to bad punctuation or spelling can turn off your audience and make you seem less knowledgeable. While you may not need to go out and buy your own AP Style Guide, it’s definitely worthwhile to review some common errors people make so you can avoid these pratfalls in your writing. Here are some of my most common faults.

That & Which

These two words are the bane of my existence, both as a writer and editor. The rules for which one to use can sound kind of complicated and textbook-y, but once you understand it, it will become second nature and improve the impact of your writing.

Let’s start with an example sentence: Do you remember the location ____ we picked?

In that sentence, would “that” or “which” be correct? The rule of thumb goes like this: if it is part of an essential clause (meaning it is necessary to understanding the meaning of the sentence), you would use “that.” If it’s a non-essential clause (if you could remove the clause and the meaning would change), use “which.” Because the meaning of the sentence is referencing a specific location (the one that was picked), it is an essential clause, and thus it should be: “Do you remember the location that we picked?”

On the other side, an example of a non-essential clause using “which” would be a sentence such as: “The shirt, which I’ve had for 4 years, is my favorite.” The meaning of the sentence is that the shirt is the speaker’s favorite – the clause about owning it for 4 years is unnecessary to understanding it. Notice that if a clause is offset by commas, it is typically non-essential.


No matter what you’re writing about, from sports to literature to adorable kitty cats, you’re almost guaranteed to have to use numbers in your writing, for whatever reason. Whether it’s to write out a statistic, an address, a date or just quoting something someone said, you’re going to need to know the proper way of writing out numbers. When you use the actual symbols for numbers (1, 5th, 1776), those are numerals. When it comes to using numerals, there are specific rules for nearly every use, from recipes to ratios and everything in between. Though you’ll likely want to consult an official AP source for your particular scenario, here are a few guidelines that will steer you in the right direction most of the time:

  • Always spell out a number at the beginning of the sentence, unless it is a number signifying a calendar year.
    • Wrong: 30 no-hitters were thrown in professional baseball last year.
    • Right: Thirty no-hitters were thrown in professional baseball last year.
    • Right: 1980 was a record year for voter turnout.
  • For ordinal uses, always spell out “first” through “ninth.” From “10th” on, use numerals.
  • When used in casual speech, always spell out number words:
    • “Thanks a million.”
    • “I’d like a quarter-pounder with cheese.”
  • When numbers are used in an adjective, connect the number and describing adjective with hyphens, and use numerals:
    • “A 100-year-old castle”
    • “6-foot-long plank of wood”

Hyphenated and Compound Words

The last two sections are fairly rule-based – meaning that once you understand the rules of essential clauses or numbers, you don’t really need to consult a resource since you’ll be able to figure it out fairly easily. Hyphens, though? Forget it – it’s the Wild West of the English frontier. This is where an AP Style Guide comes in handy, and will become the reason why you keep opening and closing your desk drawer to grab yours. What may seem like two identical words can have completely different rules for writing them.

Example: what’s the difference between “mop up” and “mop-up?”

Mop up without a hyphen refers to the verb usage, as in “The janitor will mop up the spill.” When you add that hyphen, though, it means that mop-up is now a noun or adjective, as in “The janitor did an excellent mop-up job.” Confusing? Yeah, I know, and it doesn’t stop there. That example is on the tame side of proper English writing style. It only gets worse from here.


That last bit veered off into some scary territory, huh? But it’s ok – for the most part if you can easily understand your writing without too much confusion, you’re in a good place. However, if you want to give the best impression and put more power behind your words, writing in flawless AP Style will most definitely help. Don’t think that you’re alone in that endeavor, though – I didn’t spend the past 6 years snuggled up to that AP Style Guide just to keep its juicy secrets to myself. If you want to talk about how to improve your content, or you’re ready to hand off writing to professionals, drop us a line.

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Roundpeg is an Indianapolis marketing strategy firm.