Colons are used after a complete statement to set up a list or a quote
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
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 draw attention or emphasize
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.)