Need Help with Character's Direct Thought

It can be left plain in many cases. Quotes can be more confusing than nothing at all, especially in the midst of a lot of dialog. Italics are good if the thought might be easily confused with narration, or if it needs to be emphasized. Also handy to set off a thought without using a "tag" (he thought).

He thought: Why are you dating her?

If it's already in his POV, you can simply use italics:

He starred at Jack. Why are you dating her?

Sometimes a simple shift into past tense does the trick: Why was he dating her?

It's pretty clear that that's a thought.

Dale

I was told that putting thoughts in italics is really old-fashioned. Is this not true?

Could do it by saying something like: Will wondered why Charlie was dating her.

The answer depends on what point of view you are writing in.

If third person limited and you are deep enough in the mind of the POV character to present his thoughts, the thoughts can be given in the narrative without any special attempt to distinguish them. We will assume they are the character's thoughts, just as we will assume that everything seen, heard, felt, smelled and tasted is filtered to us through the senses of the POV character.

For example:

Will shook his head. Terry was grinning like a fool just because he'd gotten his third call that morning from Annabel. She was so high maintenance. Why was he dating her?

That Terry's grin makes him look foolish, that Annabel is high maintenance, and the amazement that Terry should be dating her are all Will's thoughts.

If you're writing in omniscient point of view, hopping from character mind to character mind, you may need to attribute thoughts. As in:

The salon grew more crowded by the minute. Dmitri felt that the air would soon be sucked out of his very lungs. But Natalya whirled among the dancers as if she were a bird free in the sky. I will remember this night all my life, she thought.

Two character thoughts here: Dmitri's about his pending suffocation, given in past tense in the narrative flow; Natalya's direct thought, "quoted" in present tense and with the attribution "she thought."

Natalya's thought could also have been given so: She would remember this night all her life. However, the sentence about Natalya whirling among the dancers could be associated either with Dmitri, observing, or Natalya herself, whirling. If we assume it's Dmitri observing, then "She would remember this night all her life" could also be Dmitri's speculative observation rather than Natalya's excited internal declaration. Either way correct, the effect and meaning different. Omniscient ain't easy.

I pretty much never italicize thoughts or "quote" thoughts that can be given in the narrative flow. I like to save italics for telepathy and altered states of mind.

And, as always, check the submission guides of the house you're submitting to. Sometimes they like everything that you would put into italics to be underlined. Othertimes not. I have two publishers, and they each have their own style guide. Arg.