Social media platforms like "Twitter" are venues for 24/7 political discussion -- including deliberation, everyday banter, and bickering. For youth, these platforms offer new opportunities and risks for participation, and suggest corresponding implications for civic education. This qualitative, exploratory study examines how 15 civic youth (ages 15-25) in the United States define and carry out political dialogue on social media platforms. We compare youths' reported online dialogue strategies with strategies observed in digital artifacts of their posts. Findings suggest that youths' conceptions of good online dialogue and its key ingredients -- knowledge, respect, and diversity -- are aligned with their practices in many respects. However, juxtaposing artifacts of youths' online dialogue threads with reported strategies surfaced disjunctions, related to (1) perceived dialogue style and (2) perceptions of the value of online dialogue. Building on recent studies of novel classroom approaches, this study suggests promising entry points for educators and curricula to support youth to navigate the risks and opportunities of online spaces for civic expression and dialogue.