[Lintball]

ok i recently just got a radeon 9250 pci card..the only games i play now are halflife games i plan on getting call of duty and other low requirement games. My question is what setting should i have my card on...Open GL or D3D ? and for playing games like counter strike and call of duty should i have the settings more on performance,quality or balanced...thank you for the help also if you know of any tricks to give you better fps please fill me in, thanx