You can try what dimensive and lanofsong posted first, as its less steps than the route I take.
Here is what I do:
go to nvidia and download 346.96.
open terminal, navigate to where you downloaded the driver
chmod +x NVIDIA-Linux-x86_64-346.96.run
Now boot into recovery mode using this guide
*I don't do step 9
then switch user
then navigate to where the driver is downloaded and run
follow onscreen prompts, I always say "yes" to everything
when done, enter
You should be good to go, you can open xserver settings and verify driver version.