1. The Mark of Expectation or Addition
How to Use a Colon
The Mark of Expectation or Addition

2. Rule #1 Use a colon to introduce a series of items. Examples:
You may be required to bring many things: sleeping bags, bug spray, and marshmallows.
I need the following items from the store: butter, sugar, and flour.

3. Rule #2
Only use after statements that are complete sentences. Never use a colon after a sentence fragment.
Examples:
Incorrect: Two of my favorite hobbies are: reading and baking.
Correct: I’m fluent in two languages: profanity and sarcasm.
Notice how the items after the colon expand on or clarify what came before the colon!

4. Quick Tip
To decide whether a colon is acceptable, test whether you can replace it with the word namely.
Most of the time, if you can replace a colon with the word namely, then the colon is the right choice.
Examples:
I’m fluent in two languages, namely, profanity and sarcasm.

5. Rule #3
The same rules apply when you are writing a vertical, bulleted list.
Examples:
I have many favorite movies:
Goodfellas
Stepbrothers
Pretty in Pink
When Harry Met Sally
Don’t Be a Menace to South Central While Drinking Your Juice in the Hood

6. Rule #4
When typing, use only ONE space after a colon.

7. Rule #5
The first word after a colon is always in lowercase (unless it’s a proper name or something else that's always capitalized).