Grammar Smart 3rd Edition - Princeton Review 2014

G. Parentheses
PART 4. Punctuation

Rules For Parentheses

1. Use parentheses to enclose extra material (explanations, asides, etc.) that would otherwise interrupt the flow of the sentence.

If you go skin diving at night (an adventure for only the most experienced divers) you can observe strange and amazing phenomena.

As she whipped the cream (after making sure the ingredients were very cold) she told us she had made mousse only once before.

2. Put a period inside the parentheses if what is inside the parentheses is a complete sentence. (See Rules for Periods.)

3. Don’t put a comma after the parentheses unless the sentence would require it anyway.