Capitalization

When and what should you capitalize in written English?

Capitalize proper names and (usually) their derivatives and shortened forms.

What is a derivative? It is a word, for example an adjective, which comes from another word. The adjective English is derived from England and both are capitalized.

Here's a list of proper names and derivatives that should be capitalized:
  Names and nicknames of persons or things, trademarks Lynnea Mahlke, Statue of Liberty, Academy Award, Olympics, etc.
Geographical names America, Pacific Northwest, Seattle, Lake Washington, etc.
Peoples and their languages American, English, German, etc.
Organizations, government agencies, institutions, companies Red Cross, Congress, Cornell University, etc.
Days of the week, months, holidays Tuesday, November, Thanksgiving, etc.
Historical documents, periods, events the Constitution, Stone Age, Yalta Conference, etc.
Religions and their followers, holy books, holy days, words that stand for the Supreme Being Christianity, Hindu, the Bible, Easter, Allah, etc.
Words derived from proper names German, Americanize, Stalinism, etc.
Abbreviations and acronyms (shortened forms of capitalized words):

NATO, USA, AT&T, etc.

* There are some exceptions. We can write B.C., A.D., A.M., and P.M. (a.m. & p.m. are also possible)

Capitalize titles if they come before the person’s name, but not if they come after.

President Clinton / Bill Clinton, the president

Uncle Bill / Bill, my uncle
The words in titles of books, plays, etc. should be capitalized, except for articles (a, an, the) and conjunctions (and, but, or, for ,etc.).

The pronoun I is always capitalized.
The first word of every sentence is capitalized, as well as directly quoted speech (e.g. She said "Maybe I will come tomorrow."

Common nouns are not capitalized.

A common noun may have an indefinite article (a / an) or a word such as every or several in front of it. Compare: I would like to go to a seminar on communication skills. & I would like to go to the seminar, Communication Skills in the Workplace.

Presentations: The only rules that apply here are those for impact, style and clarity. When you prepare presentations, capitalization depends on the headlines. The most important thing is to be consistent.

Letters, Faxes, etc.: The first letter after the greeting is always capitalized in English.

Dear Axel,

How are you? I have ...