Are you doing it by hand or with a tractor?
By hand, be sure to start at the top and work your way down. Kind of the oposite of builidng it.
If your usuing a tractor, it really depends on what you have or can get. Tracks would be better over tires and a trackhoe would be the best choice possible. Especially if you had a thumb on it for clean up.
I took down an old barn with my backhoe once. It got a little scarey a few times, but mostly, it's all about planning ahead of time where you want the roof to fall and making sure your not in any danger. In my situation, I took out the corners first, then slowly worked my way around until it had colapsed all around the edges. Then I pulled out the debri and the rest of it fell in on itself.
The scary part was when I pulled one place and another place reacted. It's all connected, so what you do at one place can have an effect on another place.
Eddie