NOTE: I do not own this text (the instructions) or the site it came from *LINK IS AT THE BOTTOM OF THE POST*
Moisten a lint-free rag with a small amount of rubbing alcohol. The cloth should be damp and not soaking wet.
Hold the disc with your fingers by the rim. Avoid putting your fingers directly onto the surface of the disc.
Wipe the entire disc with the cloth. Work from the inside part of the disc where the hole is located towards the outer edge. Use a light, sweeping motion and go over the disc a couple of times to thoroughly clean it. Avoid using a circular motion or you risk damaging the disc.
Let the disc air-dry completely before putting it into the game console.
Hope this helps Antother way would to go buy disk cleaner and wipe the disk with a soft/plush rag of some sort with it.