How to use colons
Rules for use of colons
Use the colon after a complete sentence to introduce a list of items when introductory words such as namely, for example, or that is do not appear.
A colon should not precede a list unless it follows a complete sentence; however, the colon is a style choice that some publications allow.
Capitalization and punctuation are optional when using single words or phrases in bulleted form. If each bullet or numbered point is a complete sentence, capitalize the first word and end each sentence with proper ending punctuation. The rule of thumb is to be consistent.\
Use a colon instead of a semicolon between two sentences when the second sentence explains or illustrates the first sentence and no coordinating conjunction is being used to connect the sentences. If only one sentence follows the colon, do not capitalize the first word of the new sentence. If two or more sentences follow the colon, capitalize the first word of each sentence following.
Use the colon to introduce a direct quotation that is more than three lines in length. In this situation, leave a blank line above and below the quoted material. Single space the long quotation. Some style manuals say to indent one-half inch on both the left and right margins; others say to indent only on the left margin. Quotation marks are not used.
Use the colon to follow the salutation of a business letter even when addressing someone by his/her first name. Never use a semicolon after a salutation. A comma is used after the salutation for personal correspondence.