There are so many articles already written and available on the web about how to photograph christmas, that it seemed a bit pointless to write another one! Instead, I'm going to link you to some articles that I feel do a good job of both explaining how to do it and providing you with a little inspiration.
How to photograph your kids and your tree. Step by step instructions plus some seriously fantastic christmas images - use this for inspiration if nothing else.
Great tutorial for photographing christmas light displays outside.
Some great examples and some tips for beginners about taking images with light bokeh (where the lights in your image are round - see my image of the tree above)
If you like the idea of making your light bokeh into hearts or stars, there is a step by step tutorial on Kevin and Amanda's blog.
And of course Click It Up A Notch has a huge library of posts on the subject, you can see them all here.
Hope you like them!