toothpaste does work on small scratches. I'm guessing car wax or rainx would work also. However, I use a motorized disc repairer. It comes with the liquid and what amounts to an ultra fine sandpaper wheel to remove scratches. As well as a buffing cloth. Just follow the directions for whichever model you buy.
If the scratches are REALLY deep .. take the disc into a local video store. They have special machines for removing them without damaging what's on the disc.
One last thing .. if the top side (or label side) is scratched or damaged too badly ... toss the disc. There's nothing you can do, since that's where the actual information is, and that can't be fixed.