1. Punctuations outside quotation marks
American English rules state that punctuation marks such as commas, periods, and question marks, which are part of the overall sentence must be placed within quotation marks, as in the correct example above. Exemptions are punctuations marks other than commas or periods that are not part of the original statement like colons or question marks, which must be placed outside the quotation marks. For example: Was it Shakespeare who said, “The course of true love never did run smooth”?
2. Quoting words for emphasis
Sometimes, writers incorrectly put a word in quotation marks for emphasis, as if doing so has the same effect as boldface type or writing in the uppercase. Use quotation marks only when you are actually quoting speeches, sentences, or words.
3. Unnecessary comma(s)
Consider periods for long sentences spliced by commas for brevity and clarity.
4. Misplaced apostrophe
You add an “s” to make words, numbers, and abbreviations plural. Adding an apostrophe makes words possessive as in “Bella’s videos.” Apostrophes are also used to replace dropped letters in standard contractions or words, as in “‘80s,” “don’t,” and “we’re.”
5. Prolonging the sentence by combining independent clauses with a comma splice
Comma splices are the bane of run-on sentences. Your mistake when using the comma splice is that you are putting together two independent clauses that should be separated. To correct the comma splice, separate the two main ideas with a period or a conjunction followed by a comma. You may also modify the sentence construction by using a subordinating conjunction, such as after, when, or until.
6. Overusing the ellipsis
Many of us are guilty of overusing the ellipsis by mistakenly using it as a replacement for a comma, a period, or a conjunction. Sometimes it’s overused to convey a pause between thoughts, like, “Hey… I don’t want you to worry… I’m not here to deliver good news.” It’s essentially the text equivalent of filler words like “uh.”
The ellipsis originates from a Greek word that means "leave out," which is exactly what we should keep in mind before putting it to use. The ellipses is a writer’s tool used when the writer intentionally omits words. For instance, when using it in a quote that begins midsentence, “The reporter added, “…I will continue to do my job.”
7. Using a comma in place of a semicolon
Many make the mistake of using a comma to combine closely related ideas. The purpose of the semicolon is to signal a break in thought and is not as final in thought as a period. The general rule is that the two main clauses are so closely related in
8. Using consecutive exclamation points
We get that you want to seem ecstatic, especially when it’s difficult to convey proper emotion virtually, but one is enough, especially in formal writing. Save yourself the trouble of typing more and stick to just one exclamation point at the end. Anything more than one and you’ll come off as angry.
9. Confusing a hyphen with a dash
Hyphens combine two words or ideas into a single concept. Also use hyphens when spelling out some numbers like "thirty-four," a substitute for the word “to” on the topic of ranges (“5-6 hours”), and during a break in a word that continues on the following line.
Dashes may indicate an interruption in thought or speech: The host of the show started, “Tonight, we have special guests—” before the television shut down.
You may also use the dash to substitute words “it is,” “they are,” and for parentheses and commas. Remember that a dash is twice as a long as a hyphen.
10. Using an exclamation point after every sentence
This one’s not so much a grammar rule but a matter of taste. By ending every other sentence with an exclamation point, you’re deprecating this punctuation mark. To avoid this, use your exclamation points sparingly. It wouldn’t kill you to use a period once in a while.