When identifying bias in a news item, it is helpful to consider what type of news item it is. Generally speaking, most news stories contain both factual reporting and some degree of analysis.
For news outlets that adhere to journalistic integrity standards, the facts should be verifiable. One way to verify facts is to compare them among a few different news sources. This is typically fairly quick and easy to accomplish.
Bias may be found in the analysis portions of a news story. Look for loaded language, tone, and value judgments. It's also useful to consider what points of view are covered and what perspecitves may be missing.
It's important to remember that journalists are people, and that while they may strive to remain objective, their own biases or viewpoints may be present in their writing. It is also important to remember that the reputation of a news organization does not hang on a single news story. For example, the presence of a single biased opinion piece in a well-respected publication such as The New York Times or The Wall Street Journal does not render either publication totally biased and untrustworthy.
When thinking about the reputation of a news organization, it's useful to consider their track record for factual reporting alongside their political leanings. If you want to get an overview of a new organization's reputation, look them up on mediabiasfactcheck.com. That website's staff reviews news stories produced by different organizations, looking at their track record for passing fact checks, using reliable sources, using biased wording and/or misleading headlines, what stories they choose to cover, and if they have a strong political affiliation. They then rate the organization for factuality, bias, and credibility, using a format that conveys that information clearly, so you can quickly and easily get an idea of a source's reputation.