Use a colon
1). To introduce a list coming at the end of sentence
Her house has four rooms: a kitchen, a parlor, a bedroom, and a bath-room.
2). To introduce an example or an explanation related to something just mentioned
The miser had only one desire: to see his gold coins.
3). To introduce a quotation (usually of more than one line) in an essay
4). After the salutation in a formal letter
5). To seperate hours from minutes when the time of day is shown in numerals.
Misusing the Colon
Do not use a colon
1). After such as or including
All of the old gang were there, including : Mush Head, Beaver, Sparky, and Mole.- Incorrect colon use
2). Directly after a form of verb be
The three most popular composers of classical music, according to the poll, are : Bach, Mozart, and Beethoven.- Incorrect colon use
3). Between a verb and its object or between a preposition and its object.
The tourists went to: Toronto, Montreal, and Quebec.- Incorrect colon use