Another thing to think about when buying buffalo mozzarella - freshness is most important. It's also exceedingly difficult in many places to get fresh cheese given the transport time from Italy and the relatively slow turns on the shelf. If it does not have at least 6 days of shelf life left, pass it by. It's just not worth the frustration of having it turn to ricotta on top of your pizza. Also, the less fresh it is, the longer you need to drain it. I would say a minimum of 4 hours for the freshest cheese and probably at least 8 hours for something close to 7 days code remaining.
I usually slice mine and let the slices drain on 4 layers of paper towels. Look at the paper towels after a couple hours - you might need to change them. I tear the slices into marble size pieces after they have drained. If you try to tear very wet cheese into pieces, you might just get mush.