A word of warning about decorating the Christmas tree (if this is your first one): You are going to need way more ornaments than you think you do. Many people try to put a dozen ornaments on a tree, thinking that is all they are going to need, and find it looking very skimpy. Then they have to go out and buy more, only to find that it is hard to get it looking like the showcases in the catalog.
Here is how to get a showcase Christmas tree: First, the lights. A natural tree should have lights stuffed as close to the center of the tree as possible (you might not be able to bend the greens as much as you like to secure the inner lights). Artificial trees are lit as they are assembled: put the branch up, secure the light string to the inner green, run it to the outer tip, and back to the center. If you run the lights to the greens as well, it will be even more dazzling and brighter. Be warned that if you do all the greens, you will use 1,600 watts and 80 boxes of lights (50 to a box), so be prepared with plenty of spare circuits. LED bulbs are much gentler on fuses and circuit breakers, throw off less heat, and save you money. Not to mention the blown bulbs.
This is the fun part. To get a showcase, you are going to have to put ornaments into the center of the tree. Burying them might seem wasteful, but it adds interest and that 3-D effect to the tree (I tried that with mine, and it works). The good news is that you can use those crap ornaments that you really don't like or that have seen better days (not broken ones, since they are a cut hazard). The rough estimate is, for a 7-foot tree, about 140 base ornaments (the bulb type) and 70 showcase ornaments, preferably a dozen each of 6 different types of good ornaments. You will also need garland, but this need only be applied to the surface area of the tree (putting that in the interior is also an interesting option).
Your tastes should dictate the theme and colors of the tree. I have nothing against odd ornaments. Religious ornaments can be used exclusively or with other types, if one chooses. Some prefer a sparsely ornamented tree or one that has fewer lights; if that's you, then you might only need to put up 2 or 3 dozen favorites and/or as few lights as you like. And some prefer a single color or two colors running through the house (red bows and red bulbs; red-and-silver; and blue/white are popular color schemes. Personal preference is the key.
The only warning is that if you only get a few dozen ornaments and 2 or 3 sets of lights, and then expect a showcase tree, you are not going to get one. You need to get at least 20 dozen ornaments if you really want a showcase tree, plus a ton of lights. If you want a sparse tree, that is fine. But, if you want a showcase, you can start buying ornaments now (many ex-Witlesses are just starting out). It will likely cost you a thousand dollars for the tree and ornaments plus take the whole weekend to set up. But the end result could well be worth the project.