Humidity
One of the things orchids greatly appreciate is adequate humidity. Fifty percent or more is necessary, but the atmosphere in most homes, especially those with dry, hot-air heat, is far below that. Raising the humidity around orchids will result in better flowering. Some tricks to increase humidity: operate a humidifier near the plants; place the pots on flat, black pebbles set in a tray in which water is added until it almost covers the stones ("Egg crate," which is the lattice-like plastic grid sold in hardware stores for suspension ceiling lights, is a good, more steady alternative to the pebbles.); group the orchids together; or cordon off the growing area with clear plastic (but continue to provide ventilation to prevent bacteria from becoming a problem).