To keep a Christmas tree alive for longer, it's important to choose the right kind of tree. Opt for a fresh-cut tree with green needles that are not brittle or dry. Then, make sure to keep the tree in a cool, well-ventilated area away from any heat sources. Water the tree regularly, keeping the water level above the base of the trunk. Finally, make sure to trim the bottom of the trunk before placing it in the stand to help it absorb water more effectively.