Don't buy generic disks - especially those made in Taiwan. I had a 80% failure rate on dual layer DVDs (DVD+R DL, DVD-R DL are a lot harder to find). I now usually buy Mitsubishi discs, and have had 0% failure rate.
I tend to use Cd-R and DVd-R, the older format. My 7 year old Tosh DVD player plays them fine, although the manual says it will not play them!