Parentheses [( )] should surround a word or phrase given as an aside. Generally the author wants to “de-emphasize” whatever is in the parentheses while still including the information.
If the parentheses are within a sentence, don’t capitalize or punctuate the word or phrase, and don’t include the word or phrase in the subject. Example:
“I told the teacher that my dad (you’ve met him) would be a great chaperone for the field trip.”
Question marks (?) and exclamation points (!) don’t always follow this rule:
“I told the teacher that my dad (have you met him?) would be a great chaperone for the field trip.”
If the parentheses are in their own sentence, capitalize and punctuate. Example:
“I told the teacher that my dad would be a great chaperone for the field trip. (You’ve met him.)”