Periods and commas always go inside quotation marks, even inside single quotes.
The sign changed from "Walk," to "Don't Walk," to "Walk" again within 30 seconds.
She said, "Hurry up."
She said, "He said, 'Hurry up.'"
The placement of question marks with quotes follows logic. If a question is in quotation marks, the question mark should be placed inside the quotation marks.
She asked, "Will you still be my friend?"
Do you agree with the saying, "All's fair in love and war"?
Here the question is outside the quote.
NOTE: Only one ending punctuation mark is used with quotation marks. Also, the stronger punctuation mark wins. Therefore, no period after war is used.
When you have a question outside quoted material AND inside quoted material, use only one question mark and place it inside the quotation mark.
Did she say, "May I go?"
Use single quotation marks for quotes within quotes. Note that the period goes inside all quote marks.
He said, "Danea said, 'Do not treat me that way.'"
Use quotation marks to set off a direct quotation only.
"When will you be here?" he asked.
He asked when you will be there.
Do not use quotation marks with quoted material that is more than three lines in length. See Colons, Rule 5, for style guidance with longer quotes.
When you are quoting something that has a spelling or grammar mistake or presents material in a confusing way, insert the term sic in italics and enclose it in brackets. Sic means, "This is the way the original material was."
She wrote, "I would rather die then [sic] be seen wearing the same outfit as my sister."
Should be than, not then.