orthography - Best ways to write thoughts in narrative

I would normally put a thought in a narrative in quotation marks, but it becomes boring and stilted to continually write, thought Mary, or thought John. A thought normally would have a different person; e.g. "He wants to know where I was yesterday," would be the thought of the dialogue, "You want to know where I was yesterday." But in certain contexts the first example could be spoken dialogue as well. The context should give clarity, but in more complicated narrative, i.e. numerous speakers, it would not. Has anyone any hot tips for writing thoughts in dialogue.