Traditionally, Litecoins are mined with the processor of your computer (CPU. However, if your video cart is very powerful, it can also be advised to mine Litecoins with your video card (GPU). Most Graphic Processing Units actually give a better hashing rate then a CPU, certainly if your graphics card is purchased within the last 2 years. There are several GPU miners out there that are available for download, but before we get into that we need to make sure that your video card can be used for mining Litecoins. The best working video cards are the AMD Radeon Graphic Cards. If you have an other video card then don’t bother and just continue with CPU mining.
The most cost-efficient GPU to mine with is the AMD Radeon 7950, as it uses a minimum amount of electricity, and gives you a high hash rate. If you are building a mining rig, then that is the best graphics card to go with. The best Litecoin GPU mining client is Cgminer, which can be downloaded here. Now the next thing you need to do is to download the AMD APP SDK for your graphics card.

Go to this page on the AMD website, and choose your current graphics card. Download and install the SDK, and update your drivers. You can then extract the Cgminer, and fill in the worker details and server host like the example below.
I advise you to set the number of threads to the level you want to use your computer. Hit CTRL + ALT + DELETE, and go to your processes, and check how much percent the computer is in use. I adjust my settings to a level that my graphics card is used 80% by Cgminer, so it also has some space left for other tasks. I hope this guide has helped you a bit to set up your miner, and if there are any questions left, you can always ask them in the comments below.