Use the colon when the first sentence anticipates the second sentence or phrase, thereby creating an emphatic tone.
The colon provides a dramatic and somewhat underutilized way to bring a little spark to your writing. Beyond normal business correspondence (Dear Sir or Madam:), you can use the colon before quotations, formal statements and explanations. The colon enables you to highlight a semantic relationship--that is, a movement from a general statement to a specific clarification. The colon also provides a dramatic way to tease the reader's curiosity:
- As a modern ordeal by torture, litigation excels: It is exorbitantly expensive, agonizingly slow, and exquisitely designed to avoid any resemblance to fairness or justice.
You can also use the colon before an instruction or example:
- An intelligent writer knows how to polish documents: revise the document countless times.
Although usage does differ, most stylists agree that you should not capitalize the first letter after the colon unless the colon is introducing a quotation or formal statement:
- You'll be surprised by what his former employees wrote in the character report: "His attitude toward his new associates was rude and pretentious." This sentence can easily be revised:
Note that a colon must always follow an independent clause. You should never place a colon between a verb and its direct object. Incorrect: Our choices are: rescind our offer, go ahead with our plans, try to renegotiate the deal.
- We have three choices: a, b, c.
- Our choices are the following: a, b, c.
Because the colon works as the equivalent to for example or such as, it would be redundant and incorrect to write
- We have a number of options, such as: a, b, c.