Not all discs are created equal! If you value your data, then don't just go for the cheapest discs.
Here's some info you should look into.
http://www.digitalfaq.com/media/dvdmedia.htm
All those manufacturers numbers aren't listed on the brand you buy so match them up with the list here at Videohelp.
http://www.videohelp.com/dvdmedia
Also, check the disc compatibility with your recorder or writer. Here's another good list at Videohelp.
http://www.videohelp.com/dvdwriters
http://www.videohelp.com/dvdrecorders
Another easy way is before you go out and buy a bunch of discs get a 5 pack or a single disc of a certain brand to check compatibility.
I buy Memorex DVD+R 16x for backing up movies and stuff I have that aren't too important. They are medium quality discs, and you can find them for as cheap as $25 for 100 pack spindle. For more important stuff like videos I've spent hours making, I use Verbatim DVD+R or DVD-R 16x. They are top quality and you can find them as low as $30 for 100 pack spindle.