Cleaning A PS3 Disc

One of my ps3 games (NHL08) always freezes and I dont know why? There are no scratches but for some reason it always freezes. NHL games always freeze after you've had them for a while for some strange reason and am wondering how can I efficiently clean A disc. I also hear that blu-ray discs are intensely scratchproof, I beleive theres a video on youtube of a guy scraping one with various things and it still works. If true, then why does this always freeze?

warm water on a paper towel has always worked for ps2 games and cds for me. i haven't had to clean a ps3 disc yet since im very careful.

If you still have the receipt and have owned the game less than a month, you can take it back to where you bought it and exchange it for another copy of the same game.

Anyhow, I've never had to clean a disk because I always take good care of them (any time I take a game out of the console, I immediately put it back in its case).