Light - Place it near a sunny window. South, east or west facing windows are preferable to a north facing window. Poinsettias are tropical plants and will appreciate as much direct sunlight as you can provide.
Heat - To keep the poinsettia in bloom as long as possible, maintain a temperature of 65 to 70° F or 18 - 21°C during the day. Dropping the temperature to about 60°F or 16°C at night will not hurt the plant and will add to the life of the plant (keeps the colours brighter). However, cold drafts or allowing the leaves to touch a cold window can injure the leaves and cause premature leaf drop. Also, do not place near a heating vent (warm draft).
Water - Water the plant whenever the surface feels dry to the touch. Water until it drains out the bottom, but don’t let the plant sit in water (inside the decorative pot cover). Wilting is another common cause of leaf drop.
Humidity - Lack of humidity during dry seasons, in particular winter, is an ongoing houseplant problem. If your home tends to be dry and your poinsettia is in direct light, you will find yourself watering frequently. Check soil moisture before watering.