Sometimes, when writing in third person, you want the reader to know what your character is thinking. In first person you just have them (he or she) think. In third person you have to make decisions about how to do it.
You can say “he thought”, as in, “I need a boyfriend, she thought.” Or, “He thought he would go get a hamburger.” You could, but this is the narrator telling the reader what the character thought, not showing the thought, and it pulls readers away from their identification with the character.
There are times when “he thought” is best. As in, “He thought about it all morning before making up his mind.” You really don’t want to show the reader three or four hours of thought. In this case, it’s the thinking that’s important, not the thought itself.
You can use italics. “He looked into the dealer’s window. Now that’s a car I’d like to have.” But italics is more commonly used for emphasis, “It was the red car, not the green one.” How do we represent that here, when his thought is, “Now that’s a car I’d like to have.” You can’t un-italisize for emphasis in this case. Italics does have a place, when using foreign words, representing telepathy, (with roman for emphasis), and so on.
If you really want to show, not tell, or indicate, a character’s thought, the best way is to just do it.
“She sat alone in the restaurant, watching the other customers. She needed a boyfriend. At last the waiter came to take her order.” Note that its “she needed,” not “she needs,” which is the narrator commenting. Not intruding, just present in a Dickensian way. Or “I need,” which is a verbalization of her thought, and she’s feeling a need, saying the words to herself.
Most casual thought is non-verbal, despite what some experts (or “experts”) believe, that you can’t think without words. Give yourself two seconds, and think about the taste of pineapple. Now in those two seconds, what words did you use? None, you just remembered the taste, without going into a long culinary description, taken from the pages of Bon Apetite. When I want a coffee, I just get up from my chair, go into the kitchen, and make it (or wonder, why did I come into the kitchen?). I don’t think, “I guess I’ll get up from my chair…”. (Unless I’m actually talking to myself, which I do rather frequently, and answer myself too.) This is the narrator translating the non-verbal thought, which is actually something more like, “mmm, hmm, ahh”.
Note: I put punctuation where it indicates the speaking voice, not grammatical structure.
You can can say, “He thought about the taste of pineapple,” without translating or non-verbalizing. Which is why conveying a character’s thoughts takes some, um, thought on the writer’s part. So, think about it.
Thanks to Stevens Miller for reminding me about this topic.