For small and medium-sized magnets, the operator can separate them by sliding the end of the magnet off the stack by hand.

     For medium and large magnets, they can often be separated by using the edge of a table or countertop which is usually perpendicular to the magnetisation direction.

     Here is the detailed how-to: 

• -place the magnets a table top with one of the magnets hanging over the edge. 
• -use your body weight, hold the magnet(s) on the table and push down on the magnet hanging over the edge. 
• -you should be able to slide the magnets apart. 

     For very large magnets (generally 50.8mm / 2inch and larger), a specially-made magnet separating tool is required as the picture below. You'd better ask a specialist to help y ou with this. Do NOT do this if you never did it before.