We introduce the concept of "metajudgment" to provide a framework for understanding folk standards people use to navigate everyday decisions. Defined as a set of metatheories and beliefs about different types of judgment, metajudgment serves as the guiding principle behind the selection and application of reasoning strategies in various contexts. We review emerging studies on metajudgment to identify common dimensions, such as intuition versus deliberative reasoning and rationality versus reasonableness. These dimensions are examined across multiple societies. The reviewed findings illuminate an apparent paradox: Universal adaptive challenges produce largely consistent folk standards of judgment across cultures, whereas situational demands drive systematic within-person variability. Metajudgment offers a comprehensive framework for understanding diverse reasoning patterns in individual and cross-cultural contexts, calling for greater attention to the ecologically sensitive study of within-person judgmental variability.