Tuning variables: If your piano is new - Manufactures suggest tuning every quarter for the first year and every six months thereafter. If your piano has been restored and restrung - It is advised to tune your piano every quarter the first year, and every six months thereafter. Climatic changes - Changes in climate always affect the tuning stability of your piano. Playing time - Extended amounts of piano play will affect its tune.
Once moved, let the piano acclimate to its new location for about two weeks. The piano will need time to adjust after it has been moved. Tuning the piano before this acclimation time will result in an "out of tune" piano within a few days. Avoid a costly re-tune, by waiting the appropriate two weeks of rest. After the two week waiting period, have the piano expertly tuned and checked.
If you own a grand piano, you can purchase a piano cover for protection. I can provide you with a piano cover. They are available in all sizes. If you own a vertical piano, try tacking a blanket to the back side of the instrument. This will help to shield the piano from wall temperature changes. Direct sun from skylights can be extremely damaging. If this is a problem for you, try using a skylight sun shade or using a piano cover (see above). As the sun moves from season to season, monitor how the sun hits different areas in the room. The piano can then (if possible) be moved accordingly.
The room has too much Humidity - Humidity can swell all friction points, making them sluggish. The room is too dry - This can have the opposite effect causing friction points shrink. The results will be the same as having too much humidity. (If you think you are dealing with home humidity problems, my advice is to consult your professional piano technician. They can help you determine the situation and advise accordingly.) Broken jack springs Broken and/or weak spring rail springs that return the hammer to its idle position. Action (all the movement parts) - The action may need regulation and is a common ailment in all pianos. Think of it like this: Getting that major tune up on your car after 100,000 miles. A piano technician should view this for remedy.
There could be a piece of paper, or paper clip, or some object sitting on the sound board. The sound board cracked under a rib or bridge. This would be a worse case scenario, but can be repaired by a professional piano technician. (For more information about cracked soundboards, please read the problem solution below.)
Moth Balls - No piano should be without them. Regularly playing the piano - a "make sense" way to keep critters away. (no, I don't think BAD playing makes a difference. Then again...)
Wood cases should be cleaned with a soft rag with a touch of lemon oil. Polyester finishes are easily cleaned with a soft damp rag. To polish a Polyester finish piano, my best advise is to use a non silicone based paste car wax, in straight motions, not circular, and then buff if dry with a soft cloth, then a damp soft cloth to remove wax residue.