This is “Avoiding Unnecessary Commas”, section 18.2 from the book Writers' Handbook (v. 1.0).
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To use or not to use? That is the question when it comes to commas. Just as you want to be sure to use commas in all the correct places, you also want to make sure to avoid using commas when you don’t need them.
Do not use commas before a conjunction when the sentence is not compound.
No comma: Scout thinks Calpurnia is harshX and unfairly gets Atticus on her side.
Do not use a comma before the first and after the last word in a series.
No comma: The actorsX Gregory Peck, Phillip Alford, Estelle Evans, Robert Duvall, and Mary BadhamX play some of the main characters in the To Kill a Mockingbird movie.
Do not use commas around an appositive if it adds clarity, or new information, to the sentence. For example, in the following sentence, “Joey” identifies which cousin played the part.
No comma: My cousinX JoeyX once played the part of Atticus Finch.
Do not use a comma to set off an adverb clause that is essential to the sentence’s meaning. Adverb clauses are usually essential when they begin with after, as soon as, because, before, if, since, unless, until, or when.
No comma: Scout was surprised when Calpurnia kissed herX because she didn’t think Calpurnia liked her much.
Do not use a comma around a word that could be viewed as an interjection if using the comma would cause confusion or interruption in the sentence.
No comma: Scout isX basicallyX a tomboy.
Do not use a comma after although, such as, or like.
No comma: Mayella didn’t seem believable because of her actions, such asX changing her mind on the stand.
Do not use a comma after a coordinating conjunction (and, but, for, nor, or, so, and yet).
No comma: Jem called Atticus by his first name, soX it seemed natural for Jem to do it as well.
Do not use a comma along with a period, question mark, or exclamation point inside of a quotation.
No comma: “Don’t you remember me, Mr. Cunningham?X” asked Scout.
For each sentence, add and/or remove commas (replacing a comma with X) or indicate that no changes are needed.