Bright light best described by South, South East or South West facing window for majority of the species. Avoid direct sunlight.
For epiphytic orchids during the growing season water the plant when it is on the verge of drying out. From November - March reduce the watering to allow for the plants' dormant period. For terrestrial orchids during the growing season do not allow the soil to dry out. From November - March reduce the watering to the same level as epiphytic orchids.
Humidity and temperature
At the base of the plant and as part of the potting mix add sphagnum moss. When it is fairly dry to the touch mist with a fine spray using lukewarm water. Ensure there is good air circulation as sitting water on the leaves can cause fungal and bacterial decease. Do not allow the temperature to drop below 13°C (55°F).
Feeding and repotting
Use dilute specially formulated orchid feed during spring and summer. The plants will also benefit from occasional foliar feed, use a fine mister for this. Young plants will need to be potted annually, while an established plant, every other year.
Quick guide to common problems and how to deal with them.
You can find a lot more extensive advise and information on American Orchid Society website.
Aphids / Scale insect / Whitefly:
Presented as sticky, sooty deposits on stems.
Isolate the infected plant, remove any severely damaged leaves as well as blooms. Wash the leaves and stems with 1tbsp washing up liquid to 4L of lukewarm water. Use your fingernail to remove scale insects if the infestations is not too big. Repeat for two weeks in a row. Do not return the plant to join others until you've had a week without any insect sightings.
Presented as small black flies come out when the plant is moved.
Use white sticky sheets to catch the flying adults in early spring.
You can also use Neem Oil if the pests persist. Avoid applying it in direct sun and during hot days.
Dark black spots, which are soft to touch with oozing water when pressure applied.
Black rot is caused by fungi pythium and phytophthora. The fungus moves using water. Sitting water on the leaves allows the fungus to penetrate the leaf and spread through out its tissue.
Remove the plant immediately. Using a sterile knife remove all of the infected sections of the plant. When cutting away the damage give yourself a good margin of healthy tissue as a precaution. Remove all of the planting medium and allow the plant to dry thoroughly. Repot using brand new, fresh medium.
Flowers covered in tiny black spots.
This is a fungal decease called Botrytis. There is no way to remove it, but it can be controlled for the next season.
Remove any infected and dead material since this is where the fungus overwinters. Ensure the plant has good air circulation around it. When watering avoid getting the leaves wet or the plant sitting in water.