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

GRAMMATICALLY CORRECT
"I wouldn't try it," he cautioned, "unless you're quite certain you know
what you're doing."
[on its own, dialogue would not contain any internal punctuation]
"If you finish early," she suggested, "how about if we go out for coffee."
[on its own, dialogue would contain a comma in the same place]
"But I never ... ,"he faltered.
[dialogue ends in an ellipsis]
Exceptions
If the dialogue ends in a question mark or exclamation point, or is
broken off by a dash, do not add a comma.
"Bah!" he said.
"Are you sure?" she asked.
"The only thing is-" he began.
For a discussion on the distinction between ellipses and dashes,
turn to page 186.
SET OFF NONDIALOGUE QUOTATIONS WITH COMMAS
ONLY IF OTHER RULES CALL FOR IT
Other than direct speech, words may be enclosed by quotation marks
because they are a quote from some other source or a title, or are
intended to be brought to the reader's attention in a particular way.
In these cases, set the quoted element off with commas only if you
would do so if these same words were not within quotes.
For example, use commas if the quoted text is preceded by an
introductory element, if it is parenthetical or if it is part of a series:
84
According to the mediator, "a breakthrough is expected tonight."
As Dickens said, "The law is a ass."
The scene reminded me of the line by Robert Frost, "The woods are lovely,
dark and deep."
The afternoon seminar, "Planning for a Comfortable Retirement," was
already sold out.
More and more workers these days are fearful of layoffs, "rightsizing"
and pay cuts.