If it is moist, the plant does not need water. Next make sure that you do not overfertilize you plants. It is better to underfeed than overfeed. If your plant does need nutrients the leaves will turn pale and yellow. Be sure to dust the leaves of your plants to rid it from dirt, mites, and diseases.
Some people wash the leaves with soap and water.
If you choose to do this use a mild liquid soap. Cut off dead leaves and be sure to pinch and prune. Make sure your plant has plenty of light. This is one of the most important things you can give your plant to enable it to grow properly. Be sure to research the plant you own and follow the directions on how much light it needs.