Have you entered the giveaway for the designer apron yet?
The first thing you need is a tripod or a flat stable surface from which to photograph your tree. In order to get a beautiful picture of your tree without flash, you are going to need to use a really slow shutter speed, which means you will be able to see hand shake if you try taking these pictures with your camera in your hands. Ideally, you should use a tripod and the timer on the camera, so you aren't shaking the camera when you release the shutter.
Set your aperture kind of high. I know this seems counter intuitive, but unless you set your aperture kind of high, like f/11 or a little higher, you are never going to get the entire tree in focus. We will compensate for the aperture with a slow shutter speed.
I usually set my ISO between 320 and 500. Higher than I shoot portraits, but not high enough to see a distinct amount of noise. Set your shutter speed to anywhere between 1/25 to 2.5 seconds.
Focus the camera before you hit the shutter and then take your picture. Christmas trees are one of the few places where a blurry picture can be just the ticket. Try focusing your camera on something closer to you and then moving it back to your tree to take the photo.
These pictures will require quite a bit of trial and error. That is the wonderful thing about digital, you can see what you need to fix. If your pictures are too dark, drop your shutter speed more. Keeping moving your shutter speed around until you get just the picture you are looking for.
Christmas Tree photos are a bit of set up, but they are so worth it. We often use pictures of our Christmas tree that I took the year before for the background of our Christmas cards.