Firstly are we talking about production CD / DVD's or recordable?
If its recordable then the first thing i would say is that you get what you pay for. In my humble opinion i have always found TDK CD's/DVD's to be the best.
Secondly there is such a thing as Disc Rot which can be caused by oxidisation in the air and aggravated by scratches so try not to scratch the discs. Generally this only affects writable CD's / DVD's.
When cleaning a disc always use a lint-free cloth and ensure you wipe from the center straight out to the edge and not in a circular fashion. Discs are designed to withstand some scratching as long as not too much data is destroyed. this is because each segment has error correcting code included in it. Destroy to many segments in a row and it can not reproduce the original data.
Otherwise Jewel cases are generally accepted as the best method as its harder for the discs to get squashed or scratched during movement. Keep them in a dry place and away form direct sunlight (though if in a case should be ok) and away from excessive heat which could warm them.
When using a CD / DVD ensure the disc has fully stopped spinning before removing. I have had some players where i have heard the disc spinning when its been dumped back on the trolley when ejecting.
Always pick up by the edges and dont place on any surface other than the disc holder or disc drive tray.
Finally keep away from pets and children. My dog once ate its way through 10 cd's each with 10 mp3 albums on them!
p.s. Just found this online @ Life Span of DVDs
"MAM-A recommends that to improve data integrity and compatibility, burn your disks more slowly. My recommendation is to burn CDs at 16x speed and DVD's at 2x speed."