"I have never heard my piano sound so beautiful"

Proper piano maintenance begins with regular tunings.  Your piano should be tuned once a year, even if you don't use it that often.  If your piano gets a lot of use, two tunings a year will keep it sounding its best.  Regular tunings will promote stability and encourage the piano to hold the tuning longer.
 

If your piano hasn't been tuned for more than three years, it is probably quite below pitch.  This requires an extra step called a Pitch Raise.  Depending on how flat the piano is, it will need to be brought above pitch with one or more rough tunings, before performing the final fine tuning.  This ensures that the piano will hold the tuning.