Put your hair dryer on its lowest setting and direct it at the water ring. Be sure to move the dryer around so there is no direct heat and the wood doesn't overheat.
Apply a dab of either substance with a soft cloth and rub it into the mark in a circular motion. If the stain is not removed completely, apply more product and leave on for an hour or two and try again. In fact, you can leave it on as long as overnight.
Look for one that's non-gel and non-whitening, then apply it to the wood in the same direction as the grain. Remove the paste, then use a wood polish to make the surface shine.
Asking your hardware store for the finest grade steel wool available—you don't want to scratch your table. Use it to gently rub lemon oil in the wood in the direction of the grain.
It’s very good for a variety of surfaces, including wood, enamel, and Formica, and protects surfaces from moisture that causes rings in the first place.