When should I repot my orchids?
Orchids typically need to be repotted once a year. It’s time to repot your orchids when you see: 
-   Yellowing foliage 
-   Poor moisture retention and drainage 
-   Rotting or matted roots 
-   Poor growth or blooming
The best time to repot your orchids is soon after flowering or just after new growth appears.

Easy repotting directions
-   For best results, presoak orchid mix for 24-48 hours, then drain well. 
-   Shake excess potting material off the plant. Remove dead roots, and trim healthy roots to 6” to promote new growth. 
-   Use a clean pot that allows 1-2” for new root growth. Partially fill with Schultz Orchid mix, estimating where the plant will rest so that its base or crown is slightly below rim level. 
-   Position monopodial (one stem) plants in the center of the pot. Sympodial (multi-stemmed) orchids should rest against the pot wall to encourage growth toward the center. Stake if necessary to keep stems from sprawling. 
-   Add mix around the plant to cover roots and fill pot up to ¾” from the rim. 
-   Water thoroughly to settle mixture. Add more mix as needed.

Potting Materials: You can use a combination which consists of Crock (broken unglazed clay), Promix, Sphagnum moss or charcoal or a commercial Orchid Mix.

Watering: Orchids should be watered according to their individual needs but generally you must give them a heavy watering once or twice a week. Check the potting material’s moisture content with your finger. If it feels moist and cool, don’t water. If it feels dry and warm, water thoroughly by soaking the pot in room temperature water for 10 minutes. Allow water to drain thoroughly.

Lighting & Temperature: Orchids vary widely in lighting requirements. In general, provide as much bright, filtered sunlight as they tolerate without burning the leaves. Dendrobiums : 30% - 50% shade, humidity 60%-70%; Phalaenopsis : 80% shade with a high level of humidity; Oncidium : 30% - 50% shade and 60% humidity

Humidity & Air Circulation: You should mist everyday so that plant remains cool on dry days. As an alternative, fill a tray with pebbles or gravel and only enough water so the pot, resting on the gravel, will not absorb through the drain hole. Please note that although orchids such as Dendrobiums and Phalaenopsis do well indoors, air conditioning does have a “drying up” effect on them so misting the plants is the best way to replace lost moisture. The best time to water the orchids is early morning. Never over water orchids.

Feeding: Feed all orchid varieties every time you water with Orchid Food (Schultz or other type). Use as directed.

Pests & Diseases: These are best controlled by keen vigilance. Discoloring of leaves is an early indication of problems. Use only pesticides and fungicides recommended. Use of wrong chemicals could actually be more detrimental to the plant than helpful if the wrong product is used.

Information taken from www.orchidweb.org