If you just install the nvidia-driver package and do nvidia-xconfig then when you try and reboot X will fail to start with;
"(EE) No Screens Found(EE)"
The reason for this is that the dual video card arrangement that Optimus provides is not supported "out of the box". You need to do a bit of extra work to get it working.
I am assuming that you have already installed the nvidia-drivers and linux kernel headers at this stage.
Next thing to do is make sure you remove /etc/X11/xorg.conf if you already have created that by using nvidia-xconfig. In fact at this point I recommend you remove nvidia-xconfig from your system entirely.
Next install some packages;
apt-get install bumblebee bumblebee-nvidia primus
Now, it would be nice to think that would be it but we do need to edit a file to get things working;
Towards the bottom of the file in the [driver-nvidia] section change this line to look like this;
Reboot and you should be good to go.
You can test this by running this command;