To keep a Christmas tree alive, it's important to properly care for it after you bring it home. First, make sure to keep it in a cool and well-ventilated area, away from heat sources like fireplaces or heaters. Next, make sure to water it regularly, especially if it's a real tree, as they can dry out quickly. Finally, keep the tree away from pets and small children, as they can cause damage to the tree or hurt themselves by climbing on it. With proper care, your Christmas tree can stay vibrant and healthy for the entire holiday season.