Nvidia has published an extensive optimization guide
-- written by TweakGuides creator Koroush Ghazi -- for Skyrim
. It explains and advises on the PC game's standard settings (anisotropic filtering, motion blur, etc.), as well as more granular modifications involving console commands and custom initialization files. It should be immensely helpful in getting Bethesda's sprawling game looking and running as good as your system allows.
Be attentive while following the guide, though. Our game used to run so well, but we took an error to the INI.