Question

What rules (if any exist) should be followed to determine if commas, parenthesis, and hyphens should be used, in either dialogue or narration?

They seem to be pretty interchangeable and I was wondering if there is a rule to determine which is used when providing supplemental information in a sentence.

Answer 1

All are permissible.

Explanation:

You could write a sentence like "I'll pay you this much--I'm not made of money--but if you think I'm up for an open-ended blackmail arrangement (and it is blackmail!), you are quite mistaken." A court transcript of this would probably look very different: "I'll pay you this much. I'm not made of money. But if you think I'm up for an open ended blackmail arrangement, and it is blackmail, you are quite mistaken."

Ultimately, the rules of grammar and punctuation are just suggestions when it comes to writing dialogue.