For water marks and scratches, try to wipe off the mayonnaise. The oils will help lift the watermark and return the wood to its original color. If that doesn't work, try lemon oil and 0000 grade steel wool.
Wipe with the grain, using light pressure to smooth out scratches and restore color. If the watermark still doesn't come off, repaint the wood or take the furniture to a professional.
If a piece of veneer becomes loose, cut and install a new one, using wood glue. When the piece is in place, sand and stain to match the furniture.
For large gouges, butt a piece of veneer over the furniture. It may be necessary to take the part to a professional for this level of work.
If the metal drawer pulls look dull and tarnished, clean them with fine steel wool or a polishing compound. Remove the jerks, and polish them to a shine. Apply varnish to make them look good..
For light scratches, stain the wood to match the rest of the furniture. Check with a home improvement center for the proper color and apply the stain with a detail brush. After the stain dries, apply a paste wax to seal it.