Sound Advice from the Looney Tuner
 

 Polish the piano with a good quality polish --  a polish made specifically for the piano or use Old English or Lemon oil.
 

Your piano is more than a piece of furniture.  It's important to keep your piano away from direct contact with radiators, heating and cooling vents, doors, windows, and outside walls (five feet away, for best results).  Keeping the humidity level stable is equally as important.  To monitor the relative humidity changes, you may wish to purchase a wall hygrometer.  Ideally, the relative humidity should at 42 percent.  You can control this with the use of humidifiers and dehumidifiers.   Maintaining the correct environment will preserve your piano investment for a lifetime of enjoyment. Ask your piano technician for a detailed explanation.

NEVER use polish on the keys. You can clean the keys by wiping them with a clean piece of cheesecloth, lightly dampened with water. 

Never clean the interior of the piano, or attempt repairing the interior of the piano yourself. The interior of your piano should only be handled by a qualified piano technician.