glxinfo | grep 'direct rendering'
output will return "direct rendering:"
If this is 'Yes' or 'Enabled' then OpenGL is likely set up correctly. If it is listed as 'no' or 'disabled' then double check your 3D setup.
A window will be displayed with 3 rotating gears. If 3D acceleration is correctly enabled for your video card then the reported framerate should be well over 500 FPS, at the default window size. If the output shows less than 500 FPS then you should double check your 3D setup.