Though orchids have a reputation of being difficult to grow indoors, they will actually bloom for months at a time and live for years if kept in the right environment and given proper care. Typically, phalaenopsis orchids are the best variety for beginners to start with. Tropical by nature, orchids need to be surrounded by warm and humid air with plenty of indirect sunlight. They also need consistent watering and fertilizing, though they tend to require less water and food than most flowering plants.
Grow orchids in pots that have holes in the bottom for water to drain out. Rather than regular soil, the pots should be filled with a potting medium that is mostly tree bark, mixed with charcoal and perlite. Orchids naturally grow in tropical environments, and therefore need a fairly hot and humid environment. The temperature should be kept between 70 and 80°F during the day, and lowered to 60 to 70°F in the evenings so that the flowers can bloom. Humidity can be provided by using either a small humidifier or by placing a humidity tray under the plants' pots. This tray collects the water that drains off from the pots and provides humidity as the water evaporates.
Orchids require bright light, but cannot handle direct light. Place the plants near a south-facing window if possible, where they will receive plenty of indirect light. An orchid receiving the appropriate amount of light will have bright green leaves. The leaves will yellow if the plant receives too much light. Alternatively, plants that don't get enough light will have dark green leaves and no blooms.
Water the orchids every few days, so that the potting medium is just barely damp. Larger pots tend to take longer to dry out, and orchids in large pots will need to be watered less frequently. Overwatering will quickly kill an orchid, so be sure to water only when the potting medium feels dry.
Feed the orchids a balanced fertilizer once a month. Ideally, find a mix that is labeled 18-18-18, which means it contains 18% nitrogen, 18% phosphorous and 18% potassium. Since the plants need less food than most flowers, use only one-quarter to one-half the amount of fertilizer the package calls for.
Orchids should be repotted after about two years, or when long roots start to pour over the top edge of the pot. Be sure to repot the plant when it is not in bloom. Cut off any dead roots and place the plant roots-down in the center of the new pot. Fill with moist potting medium just to the bottom of the lowest set of leaves and wait to water or fertilize the plant for about one week.