you can also consult the debian wiki and try the "Debian way" although I've never tried that on a 64 Bit machine.
Make sure your sources.list includes "non-free
" so it can access the nVidia drivers from the repository
aptitude install build-essential module-assistant
m-a a-i nvidia
aptitude install nvidia-glx
Edit your xorg.conf per the directions on the how-to or nvidia readme file