To make a Christmas cactus bloom, keep the plant in a bright location that receives indirect sunlight. Make sure to water the plant regularly, but don't overwater it as that can cause the leaves to turn yellow and fall off. You should also fertilize the plant every two weeks during the growing season, and keep the temperature above 65 degrees Fahrenheit. In the fall, gradually reduce the amount of water you give the plant so that it will go into dormancy. After dormancy, the plant should begin to bloom in December.