Watering a Christmas cactus requires a bit more care than most plants. It's important to keep the soil consistently moist, but not too wet. The soil should be allowed to dry out slightly between waterings. Make sure not to overwater the plant, as this can lead to root rot and other problems. Water the Christmas cactus once a week, or more frequently during hot weather. Be sure to use room temperature water and avoid letting the soil become soggy or waterlogged. Additionally, you may want to mist the leaves with a spray bottle every few days to keep them hydrated.