Karen Runstedler from Minwax demonstrated several of their finishing and refinishing products.
Of note: if a finish is an older lacquer or shellac finish, you may be able to restore it without stripping off the old finish and without bothering the colour of the wood below. The secret is to use a product called "Furniture Restorer". It is basically a acetone based solvent that is applied with fine steel wool, very gently to the surface. This dissolves the old finish, picks up the dirt in the steel wool, and then redistributes the old finish. It is often not even necessary to add additional finish when done, but the furniture looks like new, with the same old antique colour preserved. This product has no effect on modern plastic finishes.
As shown in the photo, wipe the existing finish with a cotton swab dipped in acetone, or acetone based finger nail polish remover. If some finish comes off, the Furniture Restorer will work. If nothing comes off, you have to sand or use varnish stripper.
When that doesn't work, you need to use a paint and varnish stripper and go the whole nine yards.