Choose a site or pot with moist but well-drained soil, in full sun to partial shade. Provide shade in summer to avoid bolting (where the plant develops flowers then seeds and the taste changes).
Make sure not to plant them where other brassicas (e.g. broccoli, cauliflower, brussels sprouts, cabbage, turnips, kale, kohlrabi) have grown in the last 3-4 years to avoid disease.