There is no clear solution here, it is pure luck if you get a result or not, I recently bought a
Lite-On drive, they advertise it as being the best to read damaged disks due too it's large lens IIRC, so the actual hardware you use can make a difference to the success of reading damaged disks.
Next is the age\condition of the drive, obviously there is no clear way too know, but if the lens is dirty then reading disks may be poorer than if the lens was clean, you can buy lens cleaners quite cheaply, many supermarkets stock them these days, they come in the format of a disk, but on the "data" side it has brushes, often they come with a solution, and you apply this as per the instructions then run the disk in the drive, there is no way to see if it helps, but it can't hurt to try if you are having problems reading disks.
Finally the disk itself, this is the best starting point, as per the drive, you can buy cleaning kits, these sometimes come with a soft cloth and a bottle of liquid, you apply the liquid to the data side of the disk as per the instructions, then use the cloth to rub it in all over the disk, then polish it off, often this will make it possible to read a damaged disk, if successful retrieve the data from the disk and save it too a fresh disk.
Other solutions are similar, but have a disk housing with a handle, then after the liquid is applied you shut the lid then turn the handle, this rotates the cleaning elements around the disk similar to using the cloth, but the same rules apply, you may get lucky, or it may be too damaged to repair, on really stubborn disks it may take a few cleaning cycles before the disk will play nice, but if it still fails after all this then the disk is probably too damaged too save, hope this helps.
