For example these are all wrong:

* the meeting has finished.

* where is she?

* in 1975 Paul Allen and Bill Gates founded Microsoft

* an asterisk at the beginning of a sentence shows it is ungrammatical or wrong in some way

These should all begin with a capital thus:

The meeting has finished.

Where is she?

In 1975 Paul Allen and Bill Gates founded Microsoft.

Aside from this, the main use of a capital letter in English is with the pronoun, I:

John wanted to come but I said no.

Can I have some money please?

These, then, are the two main uses of capitalization in English: at the beginning of sentences and with the pronoun, I.

Other Capitalization in English

We also use capital letters in the middle of sentences for certain words and in certain situations. It should be remembered, however, that different style guides have different advice and you will occasionally find variations from this list.

the name of a day or a month

I’ll see you on Tuesday.

My favourite month of all is April.

the name of a language

We are all learning English.

I am learning Arabic right now.

the name of a nationality or an ethnic group

She bought an Italian coffee maker.

There are only a few Asian representatives at the conference.

proper names (including brand names)

In 1975 Paul Allen and Bill Gates founded Microsoft.

I bought the new Apple iPhone.

Note the slightly unusual capitalization of iPhone which has been done to make the name stand out; it doesn’t, however, follow the usual English rules of capitalization

the name of an historical period

We suspect this area was first settled during the Iron Age.

There was great upheaval during the Industrial Revolution.

the name of a holiday

When is Easter this year?

Will you go home for Ramadam?

a significant religious term

Are you a Buddhist?

I’ve read the Quran, but not the Bible.

the first word, and each significant word, of a title

Have you seen “The Good, the Bad and the Ugly”?

I believe Sir General John Hackett was born here.

the first word of a quotation or reported speech

Ghandi used to say, “An eye for an eye only ends up making the whole world blind.”

She said, “If you double your offer, we have a deal.”

celestial bodies

The Sun and the Moon, Mercury and Venus…

Roman numerals

Pope John Paul II was born here.

In the XIII Century.

Useful Links

The United Nations Capitalization Style Guide – a guide to capitalization as issued by the United Nations