I burn a lot of DVD's and one way that you can check after you burn them is to run the DVD through DVD Shrink. If it hangs up and ends up with a redundency error, the DVD is no good. Another way is to physically inspect the disk before you use them.
If there is a dark looking place, usually a round or oval area that is darker than the rest of the media, there's a good chance the disk is junk. Always inspect the disk again after you burn it because sometimes the dark areas will not show up until the heat of burning the disk loosens the foil from the media.
HP has a program that reads the disk for manufacturer, size of the disk, format and errors. I am at work and can't think of the name of the program right this minute, but I can post it later. One good rule of thumb is this. If you get more than a couple bad DVD's in a spindle of 100, you may want to consider checking the whole stack before burning, this way you can send the whole spindle back as a warranty.