Simple things can protect your piano from cosmetic wear. For example; avoid placing drinks, vases of flowers or pot plants on your piano as spilled liquids cause serious damage, the repair of which may amount to a major overhaul.
To keep new polyester or satin lacquer finished pianos clean, wipe them with a slightly damp cloth and dry carefully — no polish is needed. Older French polished pianos need polish reviver; apply with a clean soft cloth and then polish with a soft duster and on no account use spray polish.
Any marks on the keys which cannot be removed with a damp cloth should be left for the piano tuner to deal with.
Protect your piano from dust, especially during decorating or building work.
Make sure you have your piano regularly maintained, even consider getting it cleaned out once a year to protect you and your family from allergies.