Most ferns and orchids should be misted daily to provide the humidity they need. You can raise the humidity level around your plants by placing a humidity tray under each plant. Make a simple humidity tray by putting gravel in the saucer beneath the plant. The humidity tray will catch water after it has passed though the soil and allow it to evaporate back up into the foliage. Avoid setting plants near heating and air-conditioning vents or exterior doors.
Houseplants suffer if they receive too much or too little light.
Light is measured in foot candles, the amount of light emitted by one candle at a distance of 1'. Plants with high light requirements need at least 200 foot candles, preferring 500 or more, the amount provided by a south-facing window. Plants with very high light requirements need at least 2,000 foot candles of light. To provide that amount, you'll need to grow plants under fluorescent lights. If all your windows face north, stick with low-light plants.