A colon should be used after an independent clause to introduce a list of particulars, an appositive, an amplification, or an illustrative quotation.
A colon tells the reader that what follows is closely related to the preceding clause. It has more effect than the comma, less power to separate than the semicolon, and it is more formal than the dash. For example:
A keen footballer requires three props: boots, a ball, and his favourite team's shirt.
If the second independent clause interprets or amplifies the first, then a colon should be used to join them.
A colon can be used to introduce a quotation that supports or contributes to the preceding clause. For example:
When I dwell on the past, it helps me to think of Oasis singing: "Don't look back in anger."
A colon can also be used to:
1) Follow the salutation of a formal letter. Dear Mr. Robertson:
2) To separate the hours and minutes in time. 11:22
3) To separate the title of a work from the subtitle. Super Noodles: A guide to terrible meals.
4) To separate a bible chapter from the verse. Genesis 10:14