It is important to know that there are 2 BIG CHOICES to make. Since many orchids are epiphytes, (
http://en.wikipedia.org/wiki/E... ) they can be grown either in pots with various media (bark mix, sphagnum moss, rocks) or with little or no media with roots exposed either mounted on wood or in baskets (wood or plastic).
When an orchid is mounted, the roots need watering daily.
In pots, most orchids can be watered (well) once a week like other houseplants. So you need to chose what you are WILLING to do.
If the roots are coming out of the pot, which is common and doesn't mean you must repot them, I mist them daily so the water makes the root greener. Usually nights are cooler than day. So it's best to have them watered and wet early in the day so the roots are dry by night.