When you buy cilantro at the store, bring it home and put the cut or root ends in a glass of water
then place a light plastic bag over the top (like the bags you get from the produce section) and put it in your fridge. I keep my cilantro for 2 weeks this way. It also grows in your yard/garden easily. Give it morning sun in hot areas, or full sun on coastal or cooler areas. It will bolt when it gets too hot, but OMG the fresh garden cilantro is so aromatic and yummy.