Showing Thought in Written Form

What is the correct way to write a character’s unspoken, internal thoughts?

The following question was posed to WITS editor Barbara Milbourn.

Does the sentence below need quotation marks or should the thought line be italicized?

Staring across at the greatest entrepreneur and the richest man in the history in the world, I thought, “What do I say to this man?”

Barbara replies: This is a tough one. I have read three things [and do not remember the sources].

1. Because they are not spoken words or a quotation, they are not to have quotation marks.
2. While some authors—mostly novices—put thoughts in italics, this, too, is discouraged.
3. The idea is to write strong and clear enough that the thought reads as a thought and needs no augmentation; or you reword like: I stared across at the greatest entrepreneur—the richest man in the history of the world—and wondered what I should [might, would, could] say to him.

If you need a good editor for your nonfiction manuscript, Barbara is a great choice.