Use lots of water. We cannot stress this enough. When a Christmas tree is cut, more than half its weight is water. It is important to keep that level of water in the tree as high as possible.
Once home, place your tree in water as soon as possible. If needed, trees can be stored for several days in a cool location. Place trunk in a bucket full of water.
Use a stand that fits your tree. Avoid whittling down the sides to fit a stand. The outer layers of wood are most efficient in taking up water, and should not be removed.
Keep trees away from major heat sources.
The use of lights that produce low heat will reduce drying of the tree.
Make a fresh cut to remove about 1/2 inch from the base of the trunk. (We do this for you when you purchase a tree)
The temperature of the water does not matter and will not affect the tree's intake.
Check the stand daily to make sure the level of water does not go below the base of the tree. With many stands there can still be water in the stand even though the base of the tree is no longer submerged in water.
Never overload any circuits, always inspect your lights for signs of wear, and always turn the tree lights off when going to bed or leaving the house.