Commas set off a quotation from words used to introduce or identify the source of the quotation. A comma following a quotation goes inside the closing quotation mark.

Do not use a comma after a question mark or exclamation point.

Do not use a comma to introduce a quotation with that.

Do not use a comma with a quotation when the rest of the sentence does more than introduce or identify the source of the quotation.

Do not use a comma before an indirect quotation—one that does not use the speaker’s exact words.