A colon is most often used when introducing a list, as you can see in the following list:
1. You may be required to bring many items: sleeping bags, pans, and warm clothing.
2. I want the following items: butter, sugar, and flour.
3. I want an assistant who can do the following: (1) input data, (2) write reports, and (3) complete tax forms.
Another thing to remember is that the words before the colon must create a complete sentence.
A semicolon is used to connect two closely related ideas that each form a complete sentence.
I enjoy reading; memoirs are among my favorites.
I loved Kathryn Harrison's The Mother Knot: A Memoir; however, her memoir The Kiss was too disturbing for me.