Most people discard there poinsettias after the holidays. however, it is possible to keep the plant and get it to bloom again next season. Being able to rebloom poinsettias for several years is a great accomplishment. Use the following schedule as a reminder.
May: Cut back stems to 6-8 inches above the soil line. Repot or separate if needed. Place in a sunny window and water when soil is dry to touch. (Root cuttings if desired.)
June: Move Plant outisde. Water and fertilize more frequently as plant grows.
July 1: First Pinch. Using a clipper or fingernails, nip the center of growth of each branch of the plant taking the central stalk and leaves about 1/4 to 1/2 inch. This forces the plant to branch out.
August 15: Second Pinch. Same as above on all centers of growth.
September 1: Bring plant indoors to sunny location at 65ºF to 75ºF. Poinsettias hate drafts from windows and air vents.
October: Initiate short days (mid-December bloom date.) Water as needed and fertilize weekly according to label.
Poinsettias are what horticulturists call "short day" plants. For a short day plant to produce flowers, they must experience days with less than 12 hours of daylight. Put your poinsettia "to bed" in a closet, dark and unused spare bedroom or dark basement when you get home from work in the evening and put it back in a bright day light spot 14 or more hours later. This must happen every single day until after Thanksgiving for the poinsettia to color up and bloom.
For more information on care and handling of poinsettia plants, please click this link for expert information from the University of Minnesota Extension Service