Monologues From Plays

What is the grammer rule for punctuating inner monologue in a fictional text?

I know the rules for standard diolgue punctuation, but if a character is thinking speech in an inner monologue, how is that punctuated? Should it go within quotations, or does it merely get written in italics? Serious answers only, please. All others will be reported for point farming. Thanks.

Public Comments

1. There are three different ways you can project the inner thoughts of a character in your story. 1. Use quotations as normally done, but add tags of, "he thought etc." 2. Underline the dialogue and use no tags of, "he thought etc." 3. Italicize the dialogue and use no tags of, "he thought etc." I much prefer item #3 unless the manuscript you will be submitting may not recognize italics readily. Other authors prefer item #2.
2. I'm pretty sure it's just italicized without quotation marks. That's how I've always done it, and how I usually see it done. And it makes the most sense to me when reading it.