Capitalize the first word of a sentence. If you are quoting a full sentence, capitalize the first word of the quotation.

Kennedy said, “Let us never negotiate out of fear.”

Capitalization of a sentence following a colon is optional.

Gould cites the work of Darwin: The [or the] theory of natural selection incorporates the principle of evolutionary ties among all animals.

Capitalize a sentence within parentheses unless the parenthetical sentence is inserted into another sentence.

Gould cites the work of Darwin. (Other researchers cite more recent evolutionary theorists.)

Gould cites the work of Darwin (see page 150).

When citing poetry, follow the capitalization of the original poem. Though most poets capitalize the first word of each line in a poem, some poets do not.

Morning sun heats up the young beech tree leaves and almost lights them into fireflies

– June Jordan, “Aftermath”