Operating System: Linux Xubuntu o any linux you have
Hardware: nVidia VGA recommended with compute capability higher 2.0 - my graphics card is msi GTX 760, but works on 700 series very well.
Install packages:
1. nvidia binary driver proprietary version 340.29
2. sudo apt-get update, then sudo apt-get upgrade
3. sudo apt-get install cuda
4. sudo apt-get install nvidia-cuda-toolkit
5. sudo apt-get install gcc
6. checking correctly installed packages with:
lspci | grep -i nvidia // for graphic card
uname -m && cat /etc/*release // for OS
gcc --version // for C++ compiler
7. reboot system
8. sudo apt-get install blender - i use Blender 2.72b
9. setup Cycles Render, in File - User Preferences - System - Tab System - Compute Device select CUDA, and Save User Settings. Then close this window, and on right panel in Tab Render choose Device: GPU Compute and you have it fast render.
10. Below set Sampling - Samples for Render 100 od more, and for Preview 10 is enough. On Tab Performance select Tiles to X = 256, Y = 256.