Some of these are probably a bit late for this year:
Do not hang that treasured family heirloom ornament where the cat can reach it (or any other small critter
).
If you have little ones (of any species), don't decorate the tree with anything edible. After it's hung on the tree for a while, it's no longer edible.
Cut a half-inch (1 cm) off the bottom of the tree just before putting it in the stand, and add water immediately. That will open up the pores and let it take up the water better.
Contrary to popular opinion, some the things you're supposed to add to the water to keep the tree fresher longer do the opposite. Just use plain water, and check it DAILY. You may be surprised how much water it can take up, especially the first few days.
Don't burn wrapping paper in the fireplace.