Wait until the plant has stopped flowering to change pots. Select a plastic pot with drainage holes. If you are repotting because the orchid was root-bound, select a pot that is 1 1/2 inches wider than the previous pot.
Remove any blackened or broken roots from the orchid by cutting them away. Lower the orchid into the pot. If you are potting a divided orchid, press the cut side of the root material into the inside of the pot.
Fill the pot with orchid fir bark or sphagnum moss. Continue filling until the top of the root material is covered by the potting mix by 1/2 inch.
Firm the soil with your fingers to make sure the orchid is securely packed into the pot. Wait two days, then water until the water comes through the drainage holes in the bottom of the pot.
Repot the orchid every two years, if you have used sphagnum moss. Repot every year if you are using orchid fir bark, or whenever the roots come over the top of the pot.