answer: historical reachers use scrap books, speeches, journals, letters and diaries, photograges, audio recordings, video recordings, films, archives and manuscript material, published books, newspapers and magazine clippings published at the time.
Example: Speeches: mlk’s speech. Newspaper: news in the newspaper about Rosa parks. (Thats only two but you see where I’m going)
this is more of a personal question, i guess one example would be to study on the subject youre teaching, but like I said, this is more of a decision you would make