Grammatically Correct: The writer's essential guide to punctuation ...

"How was I supposed to-" she sputtered indignantly.
PUNCTUATION
• Do not put any other punctuation immediately adjacent to a
dash, with the exception of a question mark or exclamation point
before a closing dash. Even if the text that is broken by dashes
would otherwise take a comma or semicolon, do not include it.
She shrugged her shoulders, and he went back to arguing with the brick
wall.
She shrugged her shoulders-it was all so futile-and he went back to
arguing with the brick wall.
• Text that is enclosed within dashes may contain any punctuation
mark other than a period. Parentheses should be avoided if possible,
as the construction of an aside within an aside would be awkward.
• Do not employ both a single dash and a pair of dashes in the
same sentence, as it would then be unclear which text is enclosed by
the pair. The following sentence, for example, presents a challenge:
He had a determined goal-to bring together all the parties in the
dispute-students, faculty members and administrators-and get
them talking.
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