Accountable Sources have an explicit editorial policy and follow a code of ethics or professional standards.
Check the news source you are using for an explicit Editorial Policy.
Does it follow a Code of Ethics?
Be wary of sources that lack an explicit and prominent editorial policy or statement of ethical standards.
BBC Editorial Guidelines
The Guardian: Our Values
New York Times Standards and Ethics
NPR [National Public Radio] Ethics Handbook
American Society of News Editors (ASNE) links to individual news sources codes of ethics and newsroom practice. Three examples:
Los Angeles Times Ethics Guidelines
Hearst Newspapers: Statement of Professional Principles
Wall Street Journal: Policies for Employeess[sic] of the News Departments of The Wall Street Journal, Newswires and MarketWatch
Accountable sources issue corrections for the errors and inaccuracies they subsequently discover in their reporting.