In a small, closed jar (or another small airtight container) in a dark, dry place like a cupboard. This keeps the moisture out and prevents the spice mix from hardening. If the jar is made of dark-colored glass is even better (but not mandatory). Many people like to keep spice jars on open shelves because they look pretty, but light exposure and too much kitchen warmth are never good for spices; they will diminish their quality.