Most writers are, by nature, very good about their grammar. But there are lots of misconceptions.
☐ Grammatical errors have been eliminated.
Grammar, contrary to popular belief, does not include punctuation or spelling, as we often see on lists of “common grammatical errors,” which usually contain things like misplaced commas (punctuation) the confusion of affect for effect (usage) or misuse of apostrophes, such as it’s for its (spelling*).
Grammar concerns only the parts of speech (such as nouns, verbs, and adjectives) and how they combine to form sentences.
It’s extremely unusual to find egregious grammatical errors in the writing of people who’ve been practicing the craft for any considerable length of time. The errors we usually see are subtler ones.
Watch Your Danglers
Probably the most common grammatical problem I see is that of the misplaced dangling modifier. I believe writers know what they mean to say. Readers may even get the meaning. But when the dangler is misplaced, there is potential for a miscue, or a stumble on the part of the reader. Here’s a typical example:
As a boy, the palace guards taught him to fence.
While most readers will understand what is meant, technically, the palace guards were not a boy. Here’s what the writer meant:
When he was a boy, the palace guards taught him to fence.
Alternatively, one could also put The palace guards taught him to fence when he was a boy, depending on whether you want the emphasis on the skill or on his youth. The important thing to remember about dangling modifiers (the stuff you hang at the beginning of a sentence with a comma, whether it’s a participle or not) is this:
Phrases at the beginning of a sentence need a noun or a pronoun, and they will cling to the first one that comes along.—The BBC News Style Guide
The other major grammatical error I see has to do with keeping track of how many things you’re talking about, especially in complex sentences.
The difficulty of keeping track of all her medicines and their proper dosages were weighing on her mind.
This should actually be was weighing because, although the object of the sentence is a double-plural (medicines and their proper dosages) the subject is difficulty. The difficulty…was weighing…
Likewise, a double subject sometimes is erroneously given a single verb:
The medicines and dosages, each with its own inflammatory warning label, was too hard to keep track of.
The imposition of the singular label right before the verb distracts us from the fact that we have medicines and dosages as the dual subjects, requiring were.
Sometimes this does mean knowing how to diagram a sentence. It’s a skill worth learning.
The Chicago Manual of Style has a chapter that covers grammar, and if this is an area of weakness for you, I recommend you spend an afternoon at your local library and read it. For more detail, pick up a text like Webster’s New World English Grammar Handbook.
*—Actually, most of the time, its/it’s, there/their, and then/than mixups are typos and not errors, which is why I wish people would stop pretending that making these mistakes marks one as an idiot. They happen to everyone, honestly.