-Flat - If you are storing art, try to store it flat. I have learned that warping happens much easier if a wood canvas or canvas board is stored upright. 

-Paper - Put a piece of paper (mylar or acid-free tissue) in between artworks. 

-Keep it cool - Art can be ruined in extreme temperatures! Be sure to keep your storage space cool and dry. 

-ORGANIZE - (I don't always do this, but I wish I did) Add a flap of paper over the side that says the name of the artwork. Sometimes when you have several, you need to dig through them to find which one just sold - this saves time and hassle!