Capitalization, like spelling, is a set of conventions intended to clarify written communication. The following guidelines for capitalization are generally accepted.

Sentences should begin with a capital letter:

A boy brought home a penguin.

Proper names and adjectives derived from proper names should be capitalized:

The penguin's name was Opus.

He came from Antarctica.

He hitch-hiked across the Arctic Ocean.

Capitalize the first word of a direct quotation:

The instructor said, "Thou shalt not have fun in Physics."

Capitalize geographical names:

Vancouver Island

San Francisco

the Grand Canyon

the South Pacific

Note: do not capitalize directions that are not part of a regions name:

northern California

Capitalize the main words and the first word of the titles of articles, books, poems, plays, songs, etc.:

English Structure and Style

The Brothers Karamazov

Stairway to Heaven

Capitalize official names or names of groups or organizations:

Department of Redundancy Department

House of Commons

House of Senate

Republicans

Black Americans

Lutherans

Capitalize personifications:

Because I could not stop for Death — 
He kindly stopped for me —

Usually capitalize the first word of each line of poetic verse (see above example).