Water and Heat Marks: Apply a little mayonnaise — not salad dressing — onto the spots, spread with a finger, let it soak for a few hours to overnight. Wipe and polish the entire table to restore the shine.
Removing Difficult Marks: For even the most difficult marks such as a writing pen, mayonnaise (the all-purpose cleaner) is still the way to go, along with some Rottenstone (a mild pumice). Mix the pumice and mayo, then work the mixture into the spot in the direction of the wood grain. This may take a little time. Reapply as needed, then take a cloth to clean.