How to Punctuate with Quotations
Rule: Periods always go inside.
She said, "Not killing people is hard."
Rule 1: Commas go inside when closing a quote.
"Not killing people is hard," she said.
Rule 2: Commas go outside when introducing a quote with a dialogue tag.
Jacob asked, "Can you please untie my hands?"
Rule 3: No comma is needed when the quote is integrated (or flows) with the introductory text.
When asked to describe his attacker, Jacob replied that he couldn't because he "was blindfolded the entire time."
Rule 4: A second comma is needed after an interruption. Remember to close the first part of the quote with a comma.
"Can you please," Jacob asked, "untie my hands?"
For an abrupt interruption mid-speech, use em dashes (see below).
Questions Mark and Exclamation Mark ?!
Rule: Question marks and exclamation marks go inside only if they are part of the quote.
"I love killing people!" she yelled.
"Want me to kill him?" she asked.
Otherwise, question and exclamation marks go outside.
Did she just say "I love killing people"?
Colon and Semi-Colon
Rule: Colons and semi-colons go outside.
When I hear of senseless hate crimes, I am reminded of a quote from Shirley Jackson's short story "The Lottery": "Although the villagers had forgotten the ritual and lost the original black box, they still remembered to use stones."
Misha didn't like how he said "You're prettier when you smile"; those were the last words he ever spoke.
Note that quotations are introduced by colons (and semi-colons) when the introductory text is an independent clause (a complete sentence).
Rule 1: Em dashes go inside to show an abrupt interruption mid-speech, or a sudden change in thought or sentence structure.
"Hey, it's really nice to meet—"
"You don't look anything like your profile picture. Where are your horns? This is bullshit. I'm going home."
"Can I—may I please just use the washroom?" he begged.
Rule 2: When the quote is broken with text but doesn't signal an interruption in speech, the em dashes go out outside. You can imagine this as the narrator giving you some extra info as the character is speaking.
"May I"—his voice was hardly a whisper—"please just use the washroom."
Capital or Lower Case
Rule: If a quote is introduced mid-sentence but is part of the sentence syntactically (would flow with the sentence without the quotation marks), start the quote with lower case even if the original started with upper.
Her mother always told her that "only fools get caught."
Her grandmother reminded her to "use cold water for blood stains."
Otherwise capitalize the first letter of the quote. Only do this if the quote forms a complete sentence.
Her mother's words "Only fools get caught" repeated in her head as she sat there in the cold, dark cell.
Her grandmother's advice "Use cold water for blood stains" was all she remembered of the old lady.
Note: this still applies even if the quote was not originally the beginning of the sentence. For example, imagine the original quote from the first example was "Everyone knows that only fools get caught."