If your orchid is already potted up, there is nothing much to do except watering and fertilizing when required. If it the orchid has come to you bare root, then you need to pot it up. Select a pot that has about 2-4 inches of free space around the base, depending on the size of the plant. For example, a Dendrobium or Cattleya will only need about 2 inches of free space while a Grammatophyllum will require about 4 inches of space due to the huge size of their pseudobulbs. In effect, you are providing the plant just enough space to grow for a period of about 2 years, after which they will need to be re-potted. Select media(potting material) according to the thickness of the roots; finer media for plants with finer roots, remove any old roots, position the plant at the center of the pot, secure it with a stake and fill the pot with the remaining media so that the plant stands firm in the pot. Water thoroughly and keep aside. Do not water often until you see new roots appearing though you will need to increase the humidity around the plant.