The best way is to have your piano tuned regularly
Pianos like to be tuned regularly. If your piano is played a lot this might be every 6 months, if it is played less every year is a good idea. Why? There is approx. 20 tons of tension on the piano frame. If the piano is very flat or sharp a change to correct pitch over the whole piano will add or subtract a lot of tension on that frame! This makes strings stretch all over the place, usually unevenly and results in an unstable tune.
Pianos are designed to be held at the correct pitch (this depends on the age of the piano) and will almost always sound better and perform better at pitch.
My piano won't stay in tune for very long
All pianos go out of tune, some faster and more noticeably than others. A concert instrument is tuned for every performance and usually during the intermission as well!
If your piano is going out of tune quickly there are some common reasons that should be checked first:
It may be possible for you to simply remedy some of the above problems. A piano that is kept in a stable environment will stay in tune longer and also last longer.
Piano "Life Saver" systems
If your piano is in a less than ideal environment then consider a "Dampp Chaser Life Saver" system. These are humidity control systems that keep your piano as much as possible in a constant environment. This is a very good idea for high quality pianos! Dampp Chaser systems increase the life of the piano (the manufacturers say the piano's life is doubled) and will improve the stability of tuning.
These systems need to be installed by a piano technician else the warranty on the system is void.
If you would like more information about these systems please contact Cliff.