Your words are your most powerful weapons, and yet it’s easy to undermine yourself in verbal communication by violating some very simple rules of punctuation.

Before I dive deeper into this, a disclosure: I majored in English in college. I’ve made my living with words for almost two decades. And, I’ve made a few of these mistakes myself.

There’s no easier metaphorical way to shoot yourself in the foot. We’ve all scoffed at errors in emails and letters, wondering whether the writer even bothered to proofread. Even smart, insightful, clever people can wind up looking a little less-than-astute.

Here are 17 of the top offenses. (Know some that I missed? Let me know.)

1. Putting punctuation “outside of a quote”.

Almost never do this: “Almost never do this”. The punctuation goes inside the quote, “like this.” (Although, I’ve been told, “It’s different in England”.)

2. Commas and semicolons; not the same thing.

Use a semicolon when you want to link two independent clauses; otherwise, you probably want to use a comma.

3. Putting two spaces after a period is wrong. Like this.

If you’re over 40, or maybe even 35, you probably learned to put two spaces after a period. This is because you probably learned to type on an IBM Selectric or an Apple IIe, or maybe an Atari 2600 with an external keyboard. (Maybe even a Timex Sinclair 1000; I can go all day with these references.) Bottom line: We don’t have to do this anymore. Using two spaces after a period makes you look old.

(Disclosure:’s system keeps autocorrecting my attempt to put two spaces after a period in the subheading here, so as to demonstrate the incorrect way of doing things. That’s how wrong it is.)

4. Never use more than one exclamation point!!!

You’ll only exhaust yourself!!!

5. :-)

Emotions are cute, and they’re a good hedge against the tonal imprecision of emails. I probably use them more than I should, but they aren’t punctuation.

6. Apostrophe’s.

There are so many rules here, but in short: plurals usually don’t have apostrophes; possessives often do.

7. It’s important to learn the difference between it’s and its.

Related to Rule #6, but a common enough transgression to deserve its own entry: “It’s” is a contraction of “it is.” “Its,” on the other hand, signifies that “it” possesses something. So preserve its dignity by using its correct possessive form, or else it’s not going to look right.

8. Learn where quotes “go.”

Very often, they’re not needed. There are many websites devoted to documenting this “phenomenon” (sic).

9. Like my teacher once said, Learn to use quotes.

Notwithstanding Rule #8, if you’re including the exact words someone said, put them in quotes. If you are paraphrasing, don’t use quotes.

10. Also, fragments.

A complete sentence needs, at a minimum, a subject and a verb. In the first sentence of this paragraph, the subject is “sentence,” and the verb is “needs.” In the second sentence of this paragraph, the subject is also “sentence,” and the verb is “is;” it also contains a second clause in which the subject is “verb,” and the verb is “is.” (I’m beginning to feel like this example is more confusing than it needs to be.)

11. Don’t use run-on sentences because they go on forever and make people think that you don’t know the most basic rules of punctuation and also they just aren’t much fun to read or to write for that matter.

‘Nuff said.

12. Words, phrases, conjunctions.

“‘And,’ ‘but,’ and ‘or’ will get you pretty far.”

13. That thing when the verb don’t agree with the noun.

When the noun is singular, the verb should be singular. Same thing with plurals.

14. This thing–that you shouldn’t do.

Hyphens and dashes (“–” and “-,” or for that matter, “–“) are not the same thing.

15. If you’ve started using commas and you like them, and you’ve continued them you need to commit to them.

When I was a reporter at the military newspaper, Stars and Stripes, one of my editors said I was addicted to commas, and he was right. Either use them or don’t. (Related: missing decimals. $1,000 is not the same thing as $10.00.)

16. Also–and this is important, commas and dashes don’t go together.

The short answer here is, pick just one–and stick with it.

17. Slavishness.

If every item in this list presents you with a “no-duh” moment, congratulations. They no longer apply. The number-1 rule of punctuation is that you have to learn the rules in order to have the right to break them.