The most accurate and respectful approach is to ask what actual nation some one is. Terms like 'Native American', 'what tribe are you from', etc., are frankly way off course. The best way to explain what I am trying to get at is to refer to the word 'European'.
When I fly and land in Germany, I don't ask someone which European tribe are they frok, or, 'how do I say Hello in European?'. When I go to Italy or Sweden or the Netherlands and ask, "how do I speak European?", the response will be, " well, since you are in Italy, you speak Italian", or, "In the Netherlands we speak Dutch". No European I've ever met self-identified, nor liked being called, a tribe of Europe. Nor would most visitors think in such terms.
But for some reason the various Nationalities in what is called the Americas have all been lumped into one large ephemeral group 'called' Indian, or Native American, or First Nations. When those terms are used with the same kind of understanding that the word European is used it reflects actual learning, understanding, and respect, which appears to be the attitude those involved in these discussions aim to possess.
So forget the words Indian, first Nations, Native American. What is important is what nation, or, what nationality the person, or group, is. The more this is practiced the more I believe the overall situation is helped.
Tl;Dr. Ask someone which nation they are, NOT what tribe they are.