There are plenty of instances in which the use of a colon is necessary. Most of the time, we do it right. So rather than spend multiple paragraphs talking about those correct uses, let's examine two situations in which colons are often misused.
Please send your nominations to: Anne Jackson, ajackson@phonyemail.com.
There is absolutely no need for the colon above. In fact, it creates an artificial and disruptive separation between elements that belong together as a complete phrase, "to Anne Jackson."
Oddly, this usage is often indulged in AP style--puzzling since AP usually favors the direct and uncomplicated. But unless you're writing for a newspaper that will undoubtedly edit it back in, I'd still advise leaving it out. It's extraneous: the sentence reads just as clearly without it, and there's no grammatical basis for its use.
The corner market no longer sells: green tomatoes, spaghetti squash, or local mushrooms.
As in the previous sentence, there is no grammatical indication for the colon in the sentence above. Using it divides the sentence's parts from each other. In this case, though, the separation is more egregious since the structure that's divided is a whole predicate, "no longer sells green tomatoes, spaghetti squash, or local mushrooms." That reduces the rest to a mere fragment.
To illustrate what that division does, try removing the affected structure from each example:
Please send your nominations. [less detailed, but still grammatically complete]
The corner market. [huh?]
Probably the type of misuse seen in the second example comes from a misunderstanding of the rule to use a colon when introducing lists. But that rule actually has two parts. The colon is necessary only when a complete sentence precedes a list.
The corner market no longer sells green tomatoes, spaghetti squash, or local mushrooms.
vs.
The corner market no longer sells some specialty items: green tomatoes, spaghetti squash, or local mushrooms.
Both versions above include a list, and both are correct as written. But in the first, the list items are essential to the structure of the sentence, whereas in the second, the list provides additional detail, not words necessary to complete the thought. Try the removal test on that second sentence to prove that theory.
In short, when it comes to colons immediately following prepositions or verbs, just don't do it. While there are times that those colons are correct, they are truly few and far between. For every missing, correct one, there's a multitude of extraneous ones. If you're unsure, leave it out. It's a far more efficient use of your editor's time (as well as the money you pay that editor) to add a missing colon once than to eliminate dozens of unnecessary ones.
© 2009 by AnnaLisa Michalski