This applies to newspapers, online news, TV news segments, tweets, videos, blogs, and anything with a headline.
Read the headline. Does it trigger an emotional reaction, confirm or reflect a bias (whether yours or someone else's), or ask a question?
If yes, dismiss the headline and open the article.
Rationale: Headlines are attention-grabbing advertisements for content, not information sources.
Read the content in its entirety. Does it trigger an emotional reaction, confirm or reflect a bias, simplify a complex issue, fail to cite any legitimate sources, or use short quotes from the individual/company that's the target of the article (without the target's context provided) to lead to an opinion?
If yes, it's a blog post/opinion piece/hit piece/one-sided fragment of a larger story, and another source from another viewpoint is necessary.
Rationale: Most news stories are stories, designed to keep viewers on the site short-term and long-term through whatever means is most effective. A complete picture of the facts is the quickest way to deter most readers, who won't stick around long enough for that, and many wouldn't want to.
Is it about anything scientific, technical, political, legal, or otherwise complex?
If yes, and you're reading a news site of any kind, then you don't have the full picture. Go learn more about the subject, find the full quotes, read the research paper. Otherwise, you're still uninformed, and probably feeling an emotion about it (see above).
Rationale: Same as above, really. You're not getting the full picture, just a summary, and summaries tend to be incomplete and biased. You can do better.
Determine the general bias of the news source.
Is it left-biased? Right? Center? All the above?
Cool. Anyway, go read more articles about the subject. Read it from CNN, BBC, Fox News, Huffington Post. Find out what people are saying. Understand the spectrum and the angles. THEN form your own opinion.
Rationale: News are written by individuals. Regardless of the bias of the publication, you're dealing with people, who may impose their own bias or lack of knowledge on a subject. They, and you, aren't going to think like everybody else, and even if they're trying to be legit and diverse, they're going to miss something. If you care at all about the topic, if you want to discuss the topic, go learn about more of the angles and the slants, because that's an important part of building a true understanding of any topic.