First of all make sure you have purchased a nice healthy bundle of Cilantro. After purchasing, try not to keep it in the car for too long.
Now, remove the tag or twisty that keeps your cilantro bundled up. Place it in a glass or a container and make sure your cilantro is not touching the bottom. Fill the glass with water about 2 inches above the ends of the cilantro. When you areready to use it, just cut off the amount you will need, as if you are plucking fresh cilantro from your garden. Dump the water twice a week and refill it with new water.
And, also enjoy the beautiful green garden in your refrigerator!! :))
Thanks to Arpita for this useful tip.