I’ve been meaning to write a post about preserving herbs and spices, so I’ll start with one of the easiest: coriander.
When coriander (aka cilantro) goes to seed and the plants are brown and dry, just snip off the upper parts of the plant, leaving the seeds intact. Shake the seeds into a paper bag, and then sieve them to get rid of any debris. Store them in a glass jar (I reuse old spice jars) and in a cool, dark place. Grind with a mortar and pestle when needed.