Colons

Not sure what to do with that key to the right of "l?"

Colons and semicolons trip up the best of writers. Other than the better known uses of a colon (dates, salutations, scriptures), there are basically three reasons for typing this underused form of punctuation:

Making a list. "John went to the store. He bought a number of items: eggs, bread and milk."
Amplification of a thought. "Janet felt strongly that a list was needed: Forgetting items was a specialty of John's." Another use (for headlines or titles): "Shopping: How to do it better."
Quote. Peter said: "Don't forget the cat food."

A personal preference: In general, when a clause that can qualify as a sentence follows the colon, make it upper case. When it is a phrase or list, make it lower case. However, you will sometimes see independent clauses lower case after a colon. And, of course, in a book title, the subtitle will usually be upper case.