1.1: Parallel Punctuation
Parallel Punctuation is arguably one of the most important punctuation concepts tested in the SAT and ACT.
The rule is simple:
Parallel Punctuation Rule 1
There cannot be just 1 comma between a subject and a verb.
Between a subject and a verb, there should be 0 or 2↑commas.
Parallel Punctuation Rule 2
The punctuation marks surrounding the non-essential modifier must be parallel.

When we are separating non-essential modifiers, there are 3 ways.
Comma
Hamlet, a play written by Shakespeare, is a masterpiece.
I recently read Hamlet, a play written by Shakespeare.
*notice how only one comma is used when it comes at the end of a sentence.
Dash
Hamlet—a play written by Shakespeare—is a masterpiece.
I recently read Hamlet—a play written by Shakespeare.
*The dash usage in this way is the same as the comma usage above.
The dash has other uses as well, which will be discussed later.
Parentheses (round brackets)
Hamlet (a play written by Shakespeare) is a masterpiece.
I recently read Hamlet (a play written by Shakespeare).
*With parentheses, even when a modifier comes at the end, another must be used to close it.
Parallel Punctuation Rule 3
Within the core element of a sentence, the modifier(s) must be clearly punctuated.