Going into nvidia control panel(if you have an nvidia GPU, I don't know what to do for AMD) and setting the quality preference to performance would help a bit, also lower some settings in-game
Make sure your drivers are up to date, and close any unnecessary programs that might be using up CPU.
You could also install MSI Afterburner and overclock your GPU, but do this at your own risk because it will void any warranty and may harm your GPU if you mess up.
EDIT:Below, I did have it on my old PC, but not on this one and I'm too lazy to get it.
Last edited by Zxan; Feb 19, 2013 at 12:39 AM.