In their native tropical environment, orchids grow attached to tree canopies or rocks rather than in the soil. An orchid potting mix made of bark and charcoal will help the orchid feel at home, letting water wash over its roots and allowing for good air circulation. There are over 30,000 different varieties of orchids all around the planet, but the most common types we have in our homes are Phalenopsis, Oncidium, and Dendrobium.
Orchids like bright light, but indirect. Keep them away from sunny windowsills. The best way to water is to soak the plant thoroughly in your sink, and let it drain completely. Never leave the plant sitting in water. This can be done up to once a week when its warm, or every couple weeks when its cooler. If you notice yellowing of the leaves, reduce watering.
Orchid flowers can last for months. When all the blossoms drop off the flower stalk, trim the stalk back to its base. Often, a new flower stalk will emerge. Fertilize with a high-phosphorus (like 3-9-6) orchid fertilizer according to the directions on the label, or a high-phosphorus all-purpose fertilizer at half strength. After the orchid has finished blooming, switch to a balanced fertilizer (like 10-10-10) until you notice a new flower stalk emerging. Generally orchids bloom once a year.