Underline or italicize numbers, symbols, letters, and words which name themselves (or which are used as the figure or word).
Incorrect: "Give me a C!" the cheerleader shouted.
(The letter is used as a letter, it names itself.)
Correct: "Give me a C!" the cheerleader shouted.
Incorrect: His 2's look like 7's.
(The numbers are being referred to as figures; they are not numbering anything.)
Correct: His 2's look like 7's.
Incorrect: How do you spell shepherd?
(The sentence is not about shepherds but about the word shepherd.)
Correct: How do you spell shepherd?