I've been having discussions with people who keep finding corrupted CDs and DVDs and I thought I'd offer some advice for some people here who tend to have the same issues.
Rule 1: Never, ever, under any circumstances, touch the bottom side of the disc without having very smooth and soft fabric between your skin and the surface. Pick it up around the edges. Doubly so if it's a dual layer DVD.
Rule 2: If at all possible, keep all optical media in a hard jewel case instead of the new flimsy black plastic cases and never stack more than 2 discs ontop eachother at a time. It also has the bonus of being more compact. And never keep a writen disc in a stacked spindle.
3: If yo have to put a disc in a paper sachel, make sure the labeled side is facing through the transparent side, minimise any light that might shine on the bottom.
4: If you have to put your disc down on without putting it inside a case fisrt, allways put it face down in a shady spot like behind your monitor or under the keyboard if it's rased slightly above the table. Prevent scratches, dust and damage from light.
5: After using a disc, try and clean it with either a profesional CD care kit or just a soft and smooth cloth.
6: Never get the disc wet with any more moisture that it would receve from you blowing on it. Ever!
Follow those guidelines and I won't come around at night and slit your throaght for murdering CDs.
And OMG keep the stuff organised! Don't but a Borderlands DVD in a Jack Parrow case FFS!