The body of the letter
The style in which the body of the letter is written depends upon the kind of letter you are writing. The style or tone of a personal letter will be quite different from that of a business letter. The following hints, nevertheless, apply to letters of all kinds.

Divide the letter into neat paragraphs. Each paragraph should be an expansion of a single idea. If the letter is too short, you don’t have to divide it into paragraphs.

Write in a simple language. Use short sentences. Be clear about what you want to say and say it as directly as possible.

Before you start writing think out what you want to say. Put down your thoughts in a logical manner. While it is possible to add postscripts at the end of the letter, they are usually a sign of slovenly thinking.

Write legibly. Remember that your correspondent has to read what you write. Do not give him/her unnecessary trouble by writing illegibly.

Use proper punctuation. Put your commas and full stops in their proper places. Remember that incorrect punctuation may alter the whole meaning of a sentence.

The subscription or leave-taking
A letter must not end abruptly, simply with the writer’s name. This would look rude. So certain forms of polite leave-taking are prescribed. Examples are: Yours sincerely, Yours truly, etc.

Letters which begin Dear Sir or Dear Madam usually finish Yours faithfully. Formal letters which begin with the person’s name usually finish Yours sincerely. Informal letters may finish, for example, Yours or Love. Note that Love is not usually written by one man to another.

It is also common to put a closing formula before Yours… Common examples are: With best wishes and With kind regards.

Note that the first word of the subscription must begin with a capital letter.

Example: Sincerely yours

Signature
The signature or name of the writer should be put below the subscription. Sign with your first name or full name, but do not write any title (Mr/Miss/Dr/etc) before your name.

Example:

Yours sincerely
John Mathews

Addressing the envelope
On the envelope write the full address of the person to whom the letter is written to. While writing the address, put the first name before the surname. It is also common to write a title (Mr/Miss) before the name.

Americans usually put commas at the ends of lines in addresses; full stops may be used at the ends of addresses.
After the opening salutation, Americans may put a colon or a comma.

Note that Yours faithfully is not used in American usage. Common endings are Sincerely, Sincerely yours or Yours truly, followed by a comma.