Christmas trees can present safety problems both by drying out too quickly and by falling over.
Take a saw and make a fresh cut on the bottom just before installing the tree, just like cutting the bottom of flowers to let water in. Your tree stand should hold water or the new "water crystals", which hold water for a long time without drying out.
Make sure the tree attaches into the stand firmly. Note that almost all stands have screw holes on the outer edges. Screw this to a plywood stand almost as large as the tree branch spread and you will prevent any tipping. Very large trees should be secured with one or more "invisible" fish wire attachments near the top.