Becky Burckmyer, author of Awesome Grammar (Career Press, 2008, shares the “top 10” grammar errors she has seen in her 20-year career as a copywriter, writing coach and seminar leader:

1. Incorrect placement of quotation marks. Note that quotation marks go OUTside periods and commas, whether the little marks are part of the quoted material or not:

Archie has written a song, “Green Christmas,” which I think you should hear.

All other punctuation goes inside or outside depending on whether it’s part of the quotation. If this rule seems odd or unfamiliar, you may have been reading material published in England, where periods and commas, like all other punctuation, American or British, are in if they’re part of the quoted material, out if they aren’t.

2. Insertion of too much material between subjects and verbs. Your subject and verb should be placed close together if possible. Doing so cuts down on errors of various kinds:

The design of the spacious kitchen with its brushed steel appliances and island of granite counters the notion that functional can’t be beautiful.

Because the subject, “design,” and the verb, “counters,” are so far apart, it’s easy to misread and think the writer is discussing granite counters.

3. Misuse of the words “like” and “as.” “Like” precedes a noun, “as” precedes a verb.

In her Halloween costume, she really does look like a princess.
As you predicted, everybody wants red wine.

“Like I said” is substandard English.

4. Subject and pronoun disagreement. For example:

When a teenager turns sixteen, they can get a learner’s permit to drive.

No matter how earnestly a writer is trying to avoid gender bias, or a shower of he and she, it’s just plain incorrect to refer to a teenager as “they.” It’s possible, and advisable, to rewrite in several ways:

When teenagers turn sixteen, they can….
When you turn sixteen, you can….
Sixteen-year-olds can….

5. Omission of the serial comma. The serial comma, which guarantees you aren’t misunderstood, is the one right before the last item in a series:

The mountains are blue, huge, and imposing.

It’s not exactly an error to omit that last comma: Many organizations and publications do omit it as part of their house style, but the serial comma makes for complete clarity. If you’re not using it, readers may misunderstand and think the last two items are a unit:

The Hilton sheep are of various colors: gray, tan, gray and white, rust, black and white.

Are some of those last sheep black, some white? Or is it one group that’s both black and white? As you can imagine, in legal documents the serial comma can make a formidable difference.

6. Overreliance on the passive voice. Compare the following sentences:

Active voice: The chairman reviewed the documents.
Passive voice: The documents were reviewed by the chairman.

Note for starters that the passive voice is wordier. It’s also action-poor, since the doer of the action is no longer the subject. In fact, it causes the sentence to run in reverse, as the verb precedes the “real” subject. And it allows you to leave out the doer altogether if you choose:

The documents were reviewed.

This can be useful – for example, if you don’t know who did something, or you’re trying to protect the doer – but it can make you look shifty or tricky. In most situations, it’s desirable to avoid the passive voice if you can.

7. Misuse of the phrase “One of those….” If you’re going to use this phrase, be sure your verb agrees with the plural object, not with one:

He’s one of those poor souls who don’t have a parking space.
It’s one of those things that happen to everybody now and then.
She’s one of those people who want it all now.

In other words, of those people who want it all now, she’s one. Some people are obsessed with the notion that you can lift out that prepositional phrase “of those people” and be left with “She’s one who wants it all now.” It just isn’t so. The prepositional phrase is actually “of those people who want it all now.”

If you’re not comfortable with the plural verb, you don’t need to use this construction at all. Just rewrite: “She’s among those people who want….” or “She’s a person who wants….”

8. Dangling of participles and misplacing of modifiers. This error occurs far too often; it can produce some astounding effects:

When only six years old, his mother left the family.
Lying peacefully in the hammock, the train whistle woke me.
Exhausted and soaked to the skin, the restaurant looked warm and inviting.

Six-year-old mothers! Whistles in hammocks! Exhausted restaurants! What’s next? Take care that if you lead off your sentence with a descriptive clause such as those above, whatever follows is the subject of that clause:

When only six years old, he was abandoned by his mother.
Lying peacefully in the hammock, I was awakened by the arriving car.
Exhausted and soaked to the skin, I thought the restaurant looked warm and
inviting.

9. Subject-verb disagreement. This comes in all sorts of forms. Here’s just one example. The words with, as well as, and in addition to do not create plurals:

Mary, with her three children, hopes to be with us tomorrow.
Jack, as well as the two vice presidents, is taking the redeye to Detroit.
My husband, in addition to his brothers, is something of a packrat.

If you want those extra folks to be part of the subject, say and: “Mary and her three children hope to be with us tomorrow.”

10. Which or that. Often a comma will just “feel” right directly before “which” and not before “that”:

Which: She me a copy of Sense and Sensibility, which I devoured in one sitting.
That: She gave me a copy of the book that she’d been praising.

The issue is that which introduces a nonrestrictive clause: This clause adds information, but the sentence can stand alone without it. That introduces a restrictive, or identifying, clause: The sentence is obscure without it. (You can’t just start off a conversation or an email with “She gave me a copy of the book.”)