Identifying and labeling things is what we all do every day; it is how we communicate about the things in the world around us, e.g. “please pass the salt” or “my ticket is for seat D3”. Identifying things and assigning identifiers to them is also a fundamental part of working in the digital realm. We need to identify resources, concepts, agents, relationships, mappings, properties, namespaces, schemas, profiles, etc. Many of these have confusing subtleties of meaning, so it may help to deconstruct the identification processes we perform intuitively so we can reconstruct a sensible approach to designing our identifiers. This paper looks at how we identify things by comparing the sameness of their characteristics, how we associate symbols with things to simplify identifying them, and concludes there are six aspects that make up an identifier: a thing, a symbol, an association, a context, an agent, and a remembrance. It then considers some of the qualities of identifiers in more detail: scope, uniqueness, granularity, intelligence, actionability, persistence, extensibility, and context. It finally provides a simple checklist for designing identifiers.