We're rapidly approaching the Christmas season and that means some special plants are given extra time in the spotlight: trees, poinsettias, hollies and cactus. These are the so-called traditional Christmas plants for most of us. Don't feel that you are restricted to them. Why not take a look down your family tree and see what great, great, etc. . . . grandma and grandpa might have had in their Yuletide displays? 
Let's start with trees. It really doesn't matter which you choose, fir balsam pine, the pungent fragrance of your selection will be a welcome addition to the indoor environment.
For the tree itself there are lots of things to do to keep it at its best. And, fortunately, these steps also keep it safe. However, consider purchasing a potted tree that can be moved outside in the spring. Or try an indoor plant such as the Norfolk Island Pine. 
There is no doubt that picking out a tree is a wonderful family adventure that merits going to the lot. Here are some things you might want to keep in mind. Number one: pick a fresh tree. If you have a woodlot or legal access to one, you can ensure freshness easily. The ditch along the Wooler Road is not a public lot; nor is the verge along some out-of-the-way back road. My preference, Gentle Reader, is that you purchase your tree from a retailer who is selling a purpose-grown crop. Leave those wonderful, natural plants in their proper glory for all of us to admire. 
How do you know it's fresh? The traditional "shake it and see how many needles fall off" is still a good one. Are the needles pliable, not brittle? Look at the basal cut. Is the wood dry and beginning to turn a dull grey? Ask the merchant the harvesting history of the product. S/he'll also have on the spot advice for you. 
Second, do some measuring before you go to the lot. How tall and wide can it be? Correlate this with your doorways. Have these measurements to hand and a measuring tape in hand. When you are surrounded by hundreds of similarly appearing trees with an almost infinite variation in height and breadth, your internal scale relating house space to tree space is hopelessly overwhelmed.
Third, at home, recut the trunk at east a few inches above the original. This exposes a fresh access to the internal transport system (think arteries and veins) that will move the water throughout the tree. Your Christmas tree is a large, cut plant. What do you do when pick a bouquet of tulips or daisies? 
Fourth, don't set the tree over top of the hot air register unless it is closed off and covered. A piece of plywood or chipboard about four foot square would be ideal. Purchase a cheap, colourful "tablecloth" and staple it to the board. This will block the heat, protect the flooring, and provide a stable base for the tree holder.
Fifth, anchor the tree so it won't fall over even if the cat climbs up inside. Use a good, wide, base to set the trunk in and a bit of twine tacked into the woodwork near the top. Most air vents are below a window, most window trim has had hooks, tacks, nails and all manner of fasteners stuck into it at one time or another. For the finicky folk, use a decorative hook that matches your decor and which can be adapted to alternative uses in other seasons. A small hole in the woodwork is a wee price to pay if it prevents a precious heirloom ornament from destruction. Our precious heirlooms are cookie dough letters painted by our children when they were very young.
Fifth, give it plenty to drink. Lots of room temperature water and check daily. When fluid uptake decreases significantly it is time to move the tree out doors.
Enjoy your tree but keep safety your first priority.