1.  Dust frequently. 
2.  Use a quality furniture polish such as Guardsman's Furniture Polish.  It will lessen your chance of expensive refinishing jobs.  Polish about once a month.
3.  Clean up spills immediately.  Blot rather than wipe.
4.  For cleaning and polishing, use a soft lint-free absorbant cloth.
5.  Avoid placing furniture in direct sunlight.
6.  Avoid extremes in room humidity.  Too high or too low humidity can cause wood to warp and glue lines to fail.
7.  Avoid extreme changes in temperature.  Arrange furniture away from radiators, registers and air-conditioning units.
8.  Rotate accessories on furniture so they do not sit in the same spot all of the time.
9.  Do not place plastic or rubber things on a wood finish as their ingredients may react with those of the finish.
10.  Use pads, cloth, or felt to protect the furniture surface from plastic, rubber, hot dishes, beverages, bookends, flower pots and vases.
11.  Use a protective pad when writing with a ball-point pen.
12.  Lift objects - don't drag them across a surface.
13.  Make minor repairs while they are still small.
14.  Do not attempt to repair badly damaged surfaces without the proper materials or professional help.