Christmas cactus seem to thrive on neglect. They don't even need you to manipulate their light exposure to set buds for Christmas blooms. They are especially long lived and propagate easily from cuttings.
Light: They prefer a diffused light, although I have seen them sitting in a bright chilly window blooming profusely.
Water: Allow the soil to dry completely between waterings. Never let the soil sit wet.
Fertilizer: Feed monthly with a diluted water soluble fertilizer during spring and summer. Withhold fertilizer when the buds set and resume after flowering.
Temperature: Christmas cactus aren't fussy about temperature. Ideally they like it warm 70 - 80̊F during the growing season and cooler 55 - 65̊F while setting buds. But unless you're having difficulty getting your plant to bloom, I wouldn't worry too much about temperature.
Additional Tips: They don't like sudden drafts and will drop their buds or flowers if exposed. Keep away from frequently opened doors.
Pruning lightly after flowering re-energizes the plant.