Grow In Cool Weather
Cilantro needs cool temperatures to grow well. Cilantro will bolt (send up a flower stalk) as soon as the roots get above 75 degrees or so. This happens quick in a small 3″ pot in hot sun.
Cilantro needs to be grown in early spring or fall when the weather is cool. It requires mostly sunshine but can be grown in morning sun and shade in the hot afternoon. Growing it in the ground with mulch on top of the roots helps keep the soil cooler longer. With the best conditions Cilantro will last about 8-10 weeks before flowering. Once it does flower, it will make seeds which can be harvested as Coriander or replanted to grow more Cilantro plants.
Many people grow Cilantro by reseeding it every 3 weeks or so and have a patch growing all summer long. Planting it very close together shades the roots and helps keep it cool.
To harvest Cilantro, you can begin cutting as soon as the plant is about 6″ tall by removing the outer leaves and leaving the growing point intact for the new leaves to grow from. Another method is to wait till the plant is almost completely grown and pull it up by its roots to use the whole bunch at once.
Pick early big outer leaves first leaving small new leaves to develop, or cut all leaves above crown and a second crop will develop. If you see buds developing cut entire planet immediately