Choose a site that gets full sun. Like most herbs, coriander isn't fussy about pH, but it needs soil that's well-drained and amended with plenty of compost.
Plant coriander where you want it to grow; it quickly develops a deep taproot that doesn't respond well to transplanting.
Sow seeds 1/2 inch deep after all danger of frost has passed. When plants emerge, thin them to 4 inches apart and mulch to conserve moisture and deter weeds. Keep a close eye on young plants to make sure they don't dry out, but once established, coriander (Mediterranean native that it is) needs little water.
Ensure a steady supply of leaves by sowing succession crops every three weeks until late summer.
Harvest entire plants when they're about 6 inches high if you want only the leaves.
Wait until the seeds start to ripen, in late summer or early autumn, if they're your prime target. Cut plants off at the base and hang them upside down in paper bags to finish drying.