Your words are your most powerful weapons, and yet it's easy to undermine yourself in written communication by violating some very simple rules of punctuation.
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. Smart, insightful, clever people can wind up looking a little less than astute.
Here are 16 of the top offenses. (Know some that I missed? Let me know.)
1. Putting a period or comma "outside of a quote".
Almost never do this: "Almost never do this". A period or comma goes inside the quote, "like this." (Although, I've been told, "It's different in England".)
2. Commas and semicolons are 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: Inc.com'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!!!
Emoticons 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.
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 No. 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 No. 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 "subject" and the verb is "is"; there's also 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.
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. 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.)
15. Also--and this is important, commas and dashes don't go together.
The short answer here is, pick just one and stick with it.
If the items in this list present you with a "no duh" moment, congratulations. They no longer apply. The No. 1 rule of punctuation is that you have to learn the rules in order to have the right to break them.