the above responses are good. also, try to make a copy at a ration of 1:1; in otherwords, copy at the slowest speed. there are some CDs that just won't copy ar 4x, 6x, or whatever. It just won't work.
If, after a few tries, you can't get it to copy, move on to the next one and let it go.
If, after a few tries, you can't get it to copy, move on to the next one and let it go.