Try using these settings:

cgminer.exe --scrypt -o -u -p --shaders 1792  -I 18 -w 256 --lookup-gap 2 --thread-concurrency 21712 -g 1

or I also recommend using GUIminer -scrypt version. Still uses cgminer but has a nice GUI interface. It also has preset settings for your video cards and you can just select those and have at it.