In the wild, rather than sinking their roots into the soil, most orchids normally grow in trees, perched high above the rain forest floor. You can replicate that environment with a special orchid bark mix (a blend of ground fir-tree bark) that's sold at garden centers. It provides the quick drainage and plentiful pockets for air that orchid roots require. Mostly, though, it helps anchor plants in pots so they can grow. For best results, mix peat moss into fir bark or orchid bark mix (use 2 parts bark to 1 part peat moss), and you're ready to plant.
There are special pots on the market created just for orchids. They're full of holes to expose the roots to more air. However, a terra-cotta or plastic pot grows great orchids; no special pot is needed. Choose a pot that's 1 inch (at the most 2 inches) larger than your present pot. The time to transplant orchids is after they bloom, when new roots have appeared but haven't grown longer than 1/2 inch, or when the roots start to crawl out of the pot. Be sure to water your orchid before you repot it. Then follow this step-by-step guide to repotting and you'll have your orchid happily settled into its new quarters in no time.
Soak the pot containing the orchid in water for several hours, then gently pull out the orchid. Carefully loosen the roots, then remove the growing medium from the root ball. Replant your orchid in a pot that's only about 1 or 2 inches larger than the previous pot. Pack orchid potting mix around the roots. When the orchid is firmly in place, arrange a layer of orchid mix over the top of the roots; water well.