Anatomy of a Citation

Richard gives a blunt reply: “Chop off his head” (3.1.193).
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# Explanation
Use a colon to introducing quotations, unless grammar requires a comma.
The grammar of your sentence must fit the grammar of the quotation in tense, number, and so on. If it does not, either alter your own words, or cite a different portion of the source text.
Do not use ellipsis dots ( . . . ) at the beginnings or ends of quotations; use an ellipsis to indicate words omitted from within a quotation.
Place close-quotes before the line or page reference.
Omit any final punctuation marks from the citation except for question marks or exclamation marks. If an exclamation mark appeared in the source text, then the proper punctuation would be:

Richard gives a blunt reply: “Chop off his head!” (3.1.193).

Enclose reference information in parentheses.
Cite reference numbers up to 101 like this: 34-37; above 100, repeat only the last two figures: 211-12 (but of course, 398-402 and 99-101).
Use arabic numerals rather than roman numerals for citations of all numbered sections and subsections—books, stanzas, lines and so on: The Faerie Queene 1.6.334-42 or Paradise Lost 4.634-58.
Place final punctuation after close-parentheses to end the sentence.

This anatomy of a citation borrows heavily from Alan H. Nelson’s example citation in his Instructions for Papers. (Nelson is Professor Emeritus in the Department of English at the University of California, Berkeley)