Sentence fragments, shunned by rigid writers and grousing grammarians, often mimic speech and thus pick up the pace of your writing. Unexpected, they can command attention to strong points and comments. Here's an example from a recent New York Times article on revitalizing Starbucks:

But revitalizing the Starbucks experience is not going to be enough. Not even close.

The full sentence would have been:

But revitalizing the Starbucks experience is not going to be enough. It will not even be close.

Stripping the subject and verb from the front and leaving the fragment drives the reader straight to the point.

Here's another example from the ClearWriter archives:

The marriage of America and the rest of the world is just that. A marriage, for better or worse.

The more conventional version might have been:

The marriage of America and the rest of the world is just that, a marriage for better or worse.

A small difference, but a difference. Because the fragment is unconventional, it draws more attention to the point than the conventional version does. Just be sure that the passage merits the attention.

Like the semicolon, the colon joins in one sentence two ideas or elements that might be expressed in separate sentences, strengthening the bond. The second elements are often definitions, elaborations, or embellishments. Here's an example from The Economist€™s '€œThe day after Super Tuesday':

He [Barack Obama] also snatched two prizes on the coast: tiny Delaware and, more symbolically, Connecticut.

Note that what follows the colon needn’t be a complete sentence. Consider another example from The Economist'€™s '€œSpeaking in tongues':

Indonesia's national language'a version of Malay called Bahasa Indonesia or just Indonesian'€”is unusual in that it is not the tongue of a dominant group: only about 3% of the population are ethnic Malays.

This usage is dubious. Some style guides (AP, for example) advise against using a dash and a colon in the same sentence.

Another function of the colon is to introduce a quotation (The minority leader delivered a harsh rebuttal:) or a list, either in text (Three areas for action:) or in bullets (see below).

But colons are often misused. Here are three don'€™ts:

• Don'€™t use a colon with for example (as in I'€™ve owned all types of pets, for example: cats, dogs, lizards, and ferrets.). The colon implies for example, which should be omitted.
• Don't separate a preposition from its object (as in Over the last year I've traveled to: Arizona, New York, and Cambodia) or a verb from its objects (For dinner he ate: soup, salmon, spinach, spaghetti, salad, and sherbet.).
• Don'€™t use colons where you should use semicolons, or semicolons where you should use colons. Colons imply a direct connection between two ideas--€”and what follows the colon is subordinate to what precedes it (think of it as shorthand for that is). And remember that semicolons should generally join two ideas only if both would be complete sentences taken alone, sentences that should be parallel when possible. (LeTourneau University has a quick primer on the basic differences between colons and semicolons if you need a refresher.)