Nikon d300 pictures at night?

Shooting pictures at night of Christmas lights

Use a tripod and keep the ISO at 200 for the best images.

Set to Manual mode (or Shutter priority.)
Pick an appropriate shutter speed (maybe anything from 3 sec to 1/2 sec? - shoot and check your LCD, adjust based on what you see)
If in Manual, set Aperture to something like f/5.6. Set ISO to 200 or so to minimize grain in the picture. (if in Shutter priority, camera will set for you as its best guess.)
Use sturdy tripod to stabilize, or even set on stationery flat surface if you don't have tripod available.
Hope this helps!
Chris at www.chrisaram.com