If you were to test a burned CD, just select "Maximum," as that seems to be universally agreed upon here as the best, since it would be the fastest speed and the hardest test for a CD burn to pass. However, the scan speed for DVD will vary: if you have an NEC, 5x is the standard; if you use a BenQ of some kind, 8x. (These would be read speeds under the Burn Quality scan.) If you're speaking of actually writing a CD/DVD, I would not set the write speed to maximum. It is recommended here by several people (Rdgrimes that I can think of offhand) to burn a CD-R at 2 speed settings under it's rated speed (if it's rated for 40x, burn at 24x, for example); if it is a DVD, the best rule of thumb is to burn it at its rated speed (if it says 8x DVD, then burn at 8x). That will be enough to get you started.