The jade plant or jade tree (crassula ovata) is a succulent native to Africa. It does best in bright sun and should be allowed to dry out between waterings--the perfect house plant to place in a window and then ignore. Jade plants can survive temperatures near to freezing and will adapt to relatively low light conditions as necessary; they tend to be a forgiving plant for beginning home gardeners to experiment on.
Place your jade plant in a warm, bright window with good air circulation and as much sun exposure as possible. It may also grow well outside, as long as there is no danger of frost. If you're relocating the plant from poorly lit conditions, move it gradually to the sunnier place, or increase its time in the sunlight every day, so that it has time to adapt.
Pinch or squeeze your jade plant's lower leaves periodically to monitor its water needs. If they become soft the plant needs to be watered; wrinkled lower leaves signals urgent need for watering. Water the plant thoroughly, then let it dry out again before watering. Make sure not to leave your jade plant sitting in water; if you choose to water it from the bottom up, empty any remaining water out of the plant tray after a couple of hours.
Fertilize your jade plant, every time you water it, with a 1/4-strength low nitrogen fertilizer like 20-20-20 or 20-30-20. Watch the soil for signs like water flushing out of the pot immediately after watering, a big tight ball of roots occupying most of the soil space or very little soil being left in the container. These are all indications that it's time to repot your jade plant in a slightly larger container. When you repot the plant, place it in a mixture of one part sharp sand to two parts peat-free soil.
Prune your jade plant as needed to maintain a pleasing shape. You can trim branches all the way back to the main trunk or prune them back part-way by cutting just above the nodes on the stems. The pruned-off parts can be rooted in a dry, sandy soil if you so desire; don't water the cuttings until you see signs of root growth.
Remove dead, dropped leaves from your jade plant's pot immediately to help reduce the risk of insect infestation. Placing the plant outside to catch a gentle rain periodically, or gently rinsing it under a gentle water spray, will also help keep it clean and reduce the risk of infestation.