Asked and answered

More in comments on "Ask me anything": We'll start with the semicolon.

1. What's an easy way to remember the proper times to use a semicolon versus a period?

2. When are sentences in parentheses in sentences appropriate?

You would use a semicolon to join two independent clauses that are closely related, viz., They ask me questions; I always answer them. 

But keep in mind that it is a judgment call to use the semicolon instead of writing two sentences. The semicolon is more common in formal writing and might look stiff in yours. Some people though, like the semicolon. Nicholson Baker not only pumps for the semicolon in "The History of Punctuation" (collected in The Size of Thoughts) but also applauds the Victorian custom of combining the semicolon with the em dash. (Admire if you like, but step back.) 

An alternative to the semicolon is the comma, found in the dreaded comma-splice run-on sentence: They ask me questions, I always answer them. You do not want to do this in formal writing, and you must not say that I gave you permission to do so. But if you are writing fiction, particularly dialogue, you will find yourself resorting to this comma, because people in speech string their clauses together loosely rather than composing them, and this construction will sound more natural. 

As to the second question, about parentheses, it is best to think of them as operating like an aside in drama. The parenthetical remark is a nugget of information that is not essential to the main line of thought but is tucked in to add a bit of context. 

But writing a parenthetical clause within a sentence can be dicey, distracting the reader, viz., Nicholson Baker not only pumps for the semicolon in "The History of Punctuation" (The essay is a review of a book on punctuation collected in his The Size of Thoughts) but also applauds the Victorian custom of combining the semicolon with the em dash. See?