The easiest way to install NVIDIA GeForce Driver on Debian Linux 8 ( Jessie ) ( for Debian 9 Stretch visit: How to install the latest NVIDIA drivers on Debian 9 Stretch Linux) is to use official contrib and non-free debian repository. First, add the following non-free and contrib repositories to your /etc/apt/sources.list. Therefore, first change the content of your /etc/apt/sources.list file to include contrib and non-free packages eg.:

deb http://ftp.au.debian.org/debian/ jessie main contrib non-free
deb-src http://ftp.au.debian.org/debian/ jessie main contrib non-free

Next, update your repositories:

# apt-get update

At this point the nvidia-driver package becomes available for the installation:

# apt-get install nvidia-driver
nvidia-current:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/3.16.0-4-amd64/updates/dkms/

nvidia-uvm.ko:
Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/3.16.0-4-amd64/updates/dkms/

depmod....

DKMS: install completed.
Setting up nvidia-settings (340.46-2) ...
Setting up libegl1-nvidia:amd64 (340.65-2) ...
Setting up xserver-xorg-video-nvidia (340.65-2) ...
Setting up nvidia-driver (340.65-2) ...
Processing triggers for libc-bin (2.19-13) ...
Processing triggers for initramfs-tools (0.116) ...

During the installation you will see a notification about conflicting version of the free software nouveau nvidia driver with your currently being installed non-free nvidia kernel module which you can simply ignore.

Conflicting nouveau kernel module loaded        
                                                                     
The free nouveau kernel module is currently loaded and conflicts with the non-free nvidia kernel module.
The easiest way to fix this is to reboot the machine once the installation has finished.

Wait for the installation to finish and once done generate a new /etc/X11/xorg.conf xorg configuration file with nvidia-xconfig command. First, install nvidia-xconfig package:

# apt-get install nvidia-xconfig

After the installation is finished execute nvidia-xconfig command to generate new /etc/X11/xorg.conf config file:

# nvidia-xconfig
New X configuration file written to '/etc/X11/xorg.conf

If the above command shows message about the lack of a previous /etc/X11/xorg.conf config file simply disregard it and reboot your system to load a newly installed nvidia driver. After the reboot, login to your desktop and start the official nvidia-settings configuration tool either from command line:

$ nvidia-settings

or by starting it using a relevant menu under the start button to access more nvidia graphic card configuration settings.