Keep your instrument in a room with fairly even temperature and do not store alongside an outside wall, as the temperature changes can have a negative effect on your instruments tuning after a while.

Never store it away in a loft, garage, shed etc. as damp, cold and excessive heat may damage your instrument.

If possible store away in its case after use, or if kept out at all times store off the ground (e.g. on a chair) with a blanket draped over it, to avoid dust building up inside the instrument over time. This will eventually compromise the workings inside the instrument and result in having to get it serviced.  

Handle with care, accordions are weighty instruments and dropping them can result in costly repairs due to complex structures inside.

Avoid playing outdoors, especially in damp, cold and excessive heat conditions.