A news article (hard or soft) should have at least three sources,
and should mention each source at least once in the first half of the
Don't leave "the opposing view" until the last paragraph, because an editor will expect to be able to chop off the bottom of your story to fit it in on the page.
A movie or restaurant review is based mostly on the author's direct observations of the subject, and thus might not include any additional sources.
A news story might include quotes from
an official who makes an announcement
a member of the public reacting to the announcement, and
somebody whose reactions differs from the previous source
Depending on the nature of the story, a reporter might include balanced quotes from people on opposite sides of an issue, and a third person who is an expert in the subject matter but not involved in this particular dispute. (So, for instance, if you cover a dispute between a landlord and a tenant, you might interview the author of a book about similar cases.)
Note: For a news article, three sources is a minimum. Don't stop at 3 interview requests, and then turn in a single-source story because two people didn't return your messages.
For a routine story, professional reporters might interview a dozen people, but only quote five or six in the story. (The other interviews are to double-check what the main sources say.) Investigative reporters might have scores of contacts.