Compare a statement with the situation surrounding it. If they conflict, ask whether the contrast signals irony. Explain the effect using the context rather than assuming every negative event makes every sentence ironic.
Worked example
After waiting an hour for a service advertised as instant, a character says, 'That was instant, all right.' The context makes the literal praise unlikely and highlights frustration.
The Quiet Room
The sign promised SILENT STUDY. Inside, a printer rattled, a repair drill buzzed, and a group rehearsed a speech. Mina set down her books. 'A perfect place to hear yourself think,' she said, raising her voice over the drill. She asked the desk assistant whether another room was available, then returned the next day when repairs were finished.