I've been using a somewhat unique method for cleaning DVD's that I've never seen posted so I thought I'd share it here.
I routinely clean my DVD's before backing them up using this method and I've only had one DVD that DVDFab had trouble reading. That DVD's errors cleared up after a second cleaning.
I use a liquid spray-on coated lens cleaner, the kind you use to clean camera or eyeglass lenses. (Coated lens cleaner wipes will not work.) I also use a microfiber cloth, the kind used for polishing autos with clear-coat finishes.
The advantage of the microfiber cloth is that you can clean in a circular direction (instead of from the inside outward) because the cloth is soft enough to leave absolutely no scratches.
I spray the DVD, then rub with a 1 inch area of the microfiber cloth, then use the dry part of the cloth to polish in a circular motion (like polishing clear coat).
It works well and last a long time...