According to the Chicago Tribune, jade plants may lose leaves unseasonably because of a lack of nitrogen in the soil, from not getting enough sunlight or from being too wet or dry. Jade plants also are often attacked by mealybugs, which can be removed using a cotton swab dipped in alcohol. The Chicago Tribune recommends removing them in this way once per week, until the pests are eliminated.
The Chicago Tribune states that jade plants grow best when they get at least a half-day of direct sunlight on a daily basis. Too much moisture can be detrimental, so the Chicago Tribune advises that growers use a potting mix that drains surplus moisture quickly. If there is excess water in the plant's tray, it should be removed within 30 minutes. When the surface soil is dry, the plant can be watered again. About.com recommends that you reduce your watering habits to a monthly event during the winter months.
When repotting a jade plant, About.com recommends waiting until the roots are dry before removing the plant from the pot and knocking off the old soil and rotted or dead roots. After the jade plant has been transferred to the new pot, the roots should be kept dry for roughly a week. Then, watering can be resumed lightly. This helps to prevent root rot.