Also, know the categories of opinions:

Editorials: opinion of the newspaper's establishment/editorial board itself (for example, the NYT's endorsement of person X for president will be published as an editorial). It may or may not have anything to do with the opinion of the owners/shareholders of the paper depending on the level of journalistic independence each publication can maintain.

Op-ed (opposite the editorials): opinions of people unaffiliated with the paper, but who were actively solicited by the newspaper to write (as salaried regular columnists or one off pieces). Which again, may or may not agree with the paper's "official line" depending on the level of dissent each editorial board tolerate or on the requirements by "fair time" laws.

Letters to the Editor: unsolicited opinions (generally from readers)--which are still nevertheless curated by the editors, you are are still unlikely to see the full range of opinions "in the wild."

Semi related are Advertorials: Which are paid advertisements dressed up to to look like an op-ed or a standard news piece. These only express the opinion of whomever bought the space.