If You Don't Know When You're Using Bad Grammar, It Is Using You
I don't repudiate bad grammar. Far from it. It can be useful and I use it. It does not use me, though.
The difference between knowledgable and ignorant use of bad grammar is apparent to the educated, and using it in ignorance (absent mitigating factors such as nonnative status) will not help you reach your goals. So learn how to use it if only so that you can misuse it with impunity.
Herein the contretempsErrors of the awkward sort you seek to avoid (and that's existential).
Warning. This is a sampling of ways to misuse grammar, a taste of the most egregious offenses. Beneath a shimmering surface we will barely scratch lurk denizens of deeper realms. These will be trapped, scrutinized, tamed, and released on a regular basis. Contact me and suggest your own suspects.
Cliffhangers
Incompletes
When Only Gets Lonely
Hanging modifiers: Rich sources of reader wonderment reside herein.
Pity the perplexed reader.
A more descriptive term for this is "dangling" modifier. Lurking within a dependent phrase at the start of a sentence, it modifies the first noun in the independent clause. (Gold star if you caught the example.)
The error arises when an introductory phrase (whether participle or infinitive) modifies
that which it shouldn't.
Here's what I mean: After feeding the children, it was time
to start cooking the eggs.
Who accomplished all this? Farmer Joe? His maid? (In his dreams, perhaps.)
I know; it could have been worse: After cooking the children,
it was time to start feeding the eggs.
But that's not the point.
In either example, the introductory phrase beginning with the word after
has no subject; it was time is a noun clause implying
a subject of unknown identity. (Time was it?)
How to fix?
Either give the introductory clause a subject ("After he
fed the children"), or make Farmer Joe, the understood subject of the dependent
clause, the actual subject of the independent clause ("After feeding the
children, Farmer Joe saw that it was time ...").
The next example is worse than ambiguous; it's downright odorous: After
cleaning up the mess, the smell was still there.
We assume that someone (or something) cleaned up the mess. But the subject
of the independent clause is "smell". If it could clean up messes we might
not mind the smell. In some cases, anyway.
The actor of the introductory phrase must be the subject of the main clause,
or chaos ensues.
Cliffhangers
Incompletes
When Only Gets Lonely

Agreement in subject-verb and pronoun-antecedent:
Of the twain, the first, subject—verb agreement,
usually remains unmolested—until another noun of different number
intercedes. As in: The question that all these different
complaints bring up is whether or not in fact he slew the dragon.
Question is subject; bring
is its verb and most vehemently not in agreement with its singular subject,
question.
all these different complaints is merely
a prepositional phrase acting as an object for the preposition that
but, in the example above, successfully masquerading as a plural sentence
subject. Watch out for this breed of discord (disagreement)
when a whole lot of sentence [note: not shakin']
intervenes between subject and verb.
Disagreement between a pronoun and its antecedent can be a little more difficult
to keep at bay: When you love someone, you've got to let
them go.
Here the focus is on the pronoun them referring
back to its antecedent, someone, which you'll
notice is singular. It's a very common error, this type of disagreement,
as Sting might vouchsafe.
Hard as these are to detect, they're not that bad to disarm (unless embedded
in music). Change the number of pronoun or antecedent (but not both!) that
they may live in blissful harmony.
Another grenade. What shall it be?
Cliffhangers
Incompletes
When Only Gets Lonely

How about (not that I use them that often, she said defensively) incomplete sentences?
Sentence fragments come in two flavors: phrases
subordinate clauses
One more grenade is what kind of sentence
fragment?
That is a phrase. Actually that is not
a phrase. One more grenade is a phrase.
Phrases are easy to spot because they lack one of two things: subject or
verb. Or, in the case of prepositional phrases, both.
In addition, of course, they contain more than one word (excluding that
from the phrase category). In the example above, the whole thing is composed
of a noun phrase, one modifying more modifying the subject
of the phrase, grenade. Add one verb and we no longer have a fragment
(even of a grenade): One more grenade blew.
One final taste. Have you ever felt out of place?
Cliffhangers
Incompletes
When Only Gets Lonely

When Only Gets Lonely ...
Want to know what happens when Only gets lonely?
He gets ornery, that's what.
What that means is that when the word (adverb, actually) "only" is misplaced in a sentence, as it so very often is, it expresses its orneriness by changing the meaning of the sentence.
Consider these examples:
He only meant to open the boxes in the closet. Meaning that his only wish (for that day?) was to open boxes.
He meant to open only the boxes in the closet. Well, his intent was certainly not to open the boxes outside of the closet.
He meant to open the boxes in the only closet. It must have been a small place, having only one closet.
Not sure about where to place the 'only'? Try leaving it out. The sentence will probably work fine without it, and 'only' can no longer be lonely, in your sentence, anyway.
This 'only' feature has been an example of a wandering adverb. As a class and of course I hate to generalize, but, adverbs can be bothersome. 'Very' is one of the breed—arguably the worst of the breed. Excise it from your writing and, should you have such tendencies, bloviation will be harder put to land.
Remember the song, I Only Have Eyes for You?
Might she have wanted something in addition to eyes?
