From Sarahraven.com :
This is the leaf form of Coriander which is slower to bolt than all other forms. You can cook few Oriental meals without it and we eat the flowers and green seeds in salads. Sow little and often in the early spring and autumn, not in the hot, dry months of summer. We picked this right through the winter too last year, come frost, rain or even snow, it kept going. Highly recommended for cold weather sowing.

• EASY
• Hardy annual
• Sow: February/March and August/October
• Seeds: 100 (gave away 30)
• Sowing: Direct sow every 4-6 weeks mid-March to end of July, in blocks or lines
• Final Thinning/Planting Distance: 20-25cm
• Harvest: 4 weeks from sowing. Leaf production: 4-6 weeks.
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  Coriander is sensitive to transplanting and the shock can cause boliting so it’s best to sow in place.
  Outdoors wait till May to ensure warm soil temperatures which will promote more successful germination.
  If sowing in containers they should be at least 15cm deep for the tap root.
  Sow seeds 1cm deep, 4cm apart and cover with soil/compost. Rows 35cm apart.
  Seeds will take 2-3 weeks to germinate.

Once seedlings are 4-5cm high you can thin them down to about 20cm apart though growing close together forces them to grow upwards more quickly and produce more leaf.

Coriander should be sown every few weeks to ensure a continuous crop through the growing season

Coriander likes a lot of light but avoid middday sun as it, and temperature fluctuations, can cause bolting (which is fine if you want seeds but not if you want leaves).

Coriander will also do better in warm spots.
The soil should be well drained and have good aeration. Ensure containers have good drainage.