Colons, Semicolons and Dashes

Colons are used after a complete statement to set up a list or a quote

Examples

Andy owns videotapes of his three favorite movies: Star Wars, The Graduate, and Pee Wee's Big Adventure.
Ms. Jones expressed her frustration over the delays: "I am afraid we will have to give up the project if the board doesn't approve our permit this week."

The colon must come after a complete statement that could stand on its own as a sentence.  You would NOT do the following:

Incorrect:  Andy's favorite movies are: Star Wars, The Graduate, and Pee Wee's Big Adventure.

The colon is not needed here because "Andy's favorite movies are" is not a complete statement.  No punctuation is needed after the word "are" in this case.

Semicolons are used to join two sentences together

Examples

I really hate these shoes; they pinch my toes and give me blisters.
Brian is the fastest runner on the team; therefore, the coach as him batting lead-off.

Dashes can be used in place of commas to set of nonessential information that the writer wishes to draw attention to or emphasize

Examples

Mary won the grand prize--a baby camel--in the school raffle.
Joe is spending the weekend with his second cousin--Bill Gates.

(Note that you need to type two hyphens to make a dash.)