If multiple staffers report the story, the byline is the editor's judgment call. In general, the byline should go to the staffer who reported the key facts. Or, one staffer can take the byline for one cycle, and another for the following cycle.
A double byline or editor's note also can be used when more than one staffer makes a substantial contribution to the reporting or writing of a story. Credit lines recognize reporting contributions that are notable but don't call for a double byline.
If either of the staffers with a double byline was not in the datelined location, we should say who was where in a note at the story's end.
For roundups, the byline goes to the writer, with credit in an editor's note to the reporters who contributed substantial information.
Regarding credits for staffers who do voice or on-camera work: We do not use pseudonyms or "air names." Any exceptions – for instance, if a staffer has been known professionally by an air name for some time – must be approved by a manager.