Bruce Hamilton replies: If the damage has not worn through to the wood you may be able to improve the appearance of the surface by sanding. Start with 320 silicon carbide paper, checking the surface frequently as you sand to avoid sanding through the finish. Then move up to finer and finer grits to achieve the sheen you are looking for. You can also use 3M nylon scuffies to adjust the sheen.
Stripping all the old finish off is a messy and toxic job. If you did the original finishing yourself, you have the benefit of knowing what the original finish was. If not and something like polyester or conversion varnish was used, the old finish will be hard to strip and you may have to resort to sanding the old finish off.
After being stripped and/or sanded the surface has to be cleaned with the ammonia and water to insure there are no contaminates left behind to interfere with your new finish. The most difficult contaminations to deal with are the residues of silicone oil polishes like Pledge and Johnson Liquid Gold. Test the cleaned surface by wiping on some mineral spirits. If it beads up and does not flow out evenly, the surface is contaminated and you will have problems with the proper flow of the new finish as well as the possibility of adhesion problems. I often have to seal surfaces with de-waxed shellac to seal off the contamination. Shellac’s solvent is alcohol which is not affected by silicone.
A finishing schedule would be as follows:
If you wish to use finish that is non-toxic check, out the article in Fine Woodworking #129 called Which Finishes Are Food Safe.