This is based on the Debian way and worked for me.
This usually best done from text console not your desktop.
Stop desktop after going to console with Ctrl-Alt-F1
sudo invoke-rc.d slim stop
Check your kernel to see if you have a stock or custom kernel
uname -r
This method should work with most stock or custom kernels. For a custom kernel, you need to have its Linux headers installed.
sudo apt-get install module-assistant nvidia-kernel-common
Then to build module
sudo m-a auto-install nvidia-kernel-source
Install driver
sudo apt-get install nvidia-glx
Backup xorg.conf if you have one
sudo cp -p /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
Install Nvidia config and settings
sudo apt-get install nvidia-xconfig nvidia-settings
Run nvidia-xconfig to setup xorg.conf automatically
sudo nvidia-xconfig
Add nouveau to the blacklist
sudo nano /etc/modprobe.d/blacklist.conf
blacklist nouveau
Reboot or restart x
sudo invoke-rc.d slim restart