When should you place a colon?
Usually, the colon is used when you have made a statement and then you write specifics (often as a series) after the statement. There are good explanations and examples here:
http://grammar.ccc.commnet.edu/grammar/marks/colon.htm
One thing to remember is that you shouldn't use a colon immediately after a verb unless it's followed by a quoted phrase or sentence, as in dialogue.
=)
A colon is typically placed after a complete statement or independent clause to introduce more specific information, examples, explanations, or lists. It is important to note that a colon should not be used immediately after a verb, unless it is followed by a quoted phrase or sentence.
Here are a few examples to illustrate the usage of a colon:
1. Example of introducing a list:
I went to the grocery store and bought the following items: eggs, milk, bread, and cereal.
2. Example of introducing an explanation:
She had only one solution to the problem: to start over from scratch.
3. Example of introducing an example:
The dress code is simple: no jeans, sneakers, or t-shirts.
4. Example of introducing a quotation:
He shouted, "The time for change has come: we must rise up and fight for our rights!"
It is always helpful to refer to a trusted grammar resource, like the one you mentioned (http://grammar.ccc.commnet.edu/grammar/marks/colon.htm), for more detailed explanations and further examples.