Overwatering
          Overwatering is the most common reason why beginners have difficulty growing orchids.  Overwatering can kill plants because the constant moisture suffocates the roots, thereby causing them to die and rot.  Roots need both water and air.  That is why constant watering or standing water is extremely harmful to your orchid.  Some orchids will in fact put out roots for the sole purpose of breathing.  These roots sprout from the the base of the plant and can eventually hang out off the edges of the pot.  Please, don't cut these roots, the plant uses them to breathe.

"When should I water?"
          Knowing when to water can be difficult for those who have never owned orchids.  It can be even more confusing for those who own different types of orchids.  However, there are some general guidelines you can follow to know when you should water.
          For beginners, we typically suggest watering 1 time a week.  As your learn more about your orchids, you may find that you need to increase or decrease how often you water.  However, under no situation will you find yourself watering every day.  
          Orchids should be watered in the morning.  This allows excess water to evaporate.  Allowing excess water to remain can often lead to all sorts of problems such as root rot, plant diseases, or deterioration of the potting material.  
           Although orchids are tropical plants, they usually grow on trees and dry out somewhat between periods of rain.  (It is actually humidity that they like.)  For orchids with pseudobulbs, such as Cattleyas, you should should allow the potting material to dry between waterings.  Exceptions are orchids without pseudobulubs, such as phalaenopsis, which can be watered when the potting material is still a little moist.  This is why we suggest 1time per week for starters. Note: During cooler months, you will probably find that you do not need to water as often.

"How should I water and what kind of water should I use?"
          The best way to water your orchids is by ensuring that the potting material is thoroughly soaked.  This can be done by pouring water throughout the pot or by dunking the pot in a bath of water.  In either case, excess water should be allowed to drain.  Soaking the potting material ensures that all the roots will receive adequate moisture.
          You should water your orchid plants with luke-warm or room-temperature water.  Cold water can often shock the plants roots.  Be very careful not to use "softened" water.  Softened water makes use of salts that introduce sodium into the water making it harmful to plants.  Tap water is usually fine as long as the amounts of minerals are not high.  Ideally, distilled or rain water is best because of the lack of any minerals or impurities.