Phalaenopsis
Light: Low light, East facing window is best
Water: Once a week if potted in bark. Let the plant dry out between waterings if planted in other medium. Let water drain completely from pot.
Fertilize: Those planted in bark need a fertilizer with a higher Nitrogen amount i.e. 30-10-10. Those planted in other medium can use an all purpose fertilizer (20-20-20). Feed them monthly after watering.
Dendrobium
Light: High light but not direct light. A lightly shaded South window is best. A warmer environment is necessary for this variety as well.
Water: Keep moist during active growth; let them dry out between waterings while they are flowering.
Fertilize: Feed when not in bloom, weekly with a 1/4 strength 20-20-20 fertilizer.
Both orchid varieties benefit from some humidity. Place pot on a dish of pebbles filled with water.
images courtesy of Canadian Company Paramount Orchids