In summer, when they are outdoors, citrus trees need water almost daily. When grown indoors, their soil should be allowed to dry to the touch between waterings. Do not allow them to stand in water after the pot has drained into the saucer. They like slightly cooler temperatures than the average home. Citrus need high humidity, especially when blooming.
Low humidity is often a reason for dropping blooms and fruit.
Mist them daily, stand them on a pebble tray full of water or use a humidifier. Citrus should be fed three times a year, early spring, early summer and late summer. They prefer an acid fertilizer applied no stronger than the recommended rate. A potting soil designed for African violets suits them well. Just be sure it is well-drained.