You can have a really good Video card, but whats the use if you haven't tweaked it for performance. Dont just settle for the defaults that Windows or your Video card manufacturer sets you up with when you first install it, tweak it!
Lets go through some obvious and not so obvious areas you want to check and do some adjustments.
The focus of Video card tweaking is getting the most your PC can handle from specific Direct3D
and OpenGL settings. There are many other areas starting from the BIOS, Overclocking to adjusting Windows Memory settings that can also improve performance, however the easiest and most noticable tweak starts at your video cards driver and setup level. For this reason, whether you have a Nvidia or ATI chipset the bottom line is always having the latest drivers installed if possible and then tweaking them.
I'll use examples that are essentially applicable to both ATI and Geforce Cards since these are the majority types used on the market.
First thing to do is access the "Advanced" settings of your Video card.
As you can see here when you open the Display settings in Windows to access the ATI Catalyst Driver settings it is set to "Basic" change it to "Advanced" so we can tweak it.
Similarly if you have a Geforce Card make sure you select the "Advanced 3D settings option".
You will then be able to access a similar screen like this: