There are many types of fresh Christmas greenery that are commonly used by flower shops to produce table, mantle and door decorations.
English Holly is very popular and is actually grown on holly farms to be culivated especial for use in the floral industry around the holidays.
Although the coloring may vary from being grown at different farms and soils, the leaves are usually a glossy dark green with and underside of a lighter green.
Red berries may accent and contrast with the leaves. Be cautious when using English holly, since the spiny tips on the edges can be rather sharp and cut fingers if you are not careful.
You can snip off the spiny barbs with the tips of floral scissors (which I find easier than cutting with a floral knife) if you desire.
As a florist, I rarely used solid holly in an arrangement. Instead, I like using a combination of holly mixed with other Christmas greens, including seeded eucalyptus, white pine, spruce, fir, cedar and more common year round greenery such as leather leaf fern, boxwood, salal tips, and (for longer lines) myrtle and Italian ruscus.
Fresh holly is available in bulk, but must be shipped overnight and then stored in a very cool area (such as a garage) to maintain freshness for as long as possible.
Greening techniques are the same as for all year centerpieces, except you substitute evergreens for some of the more common greenery.
I have several step by step tutorials Christmas centerpiece tutorials available