hold your leather one in your arm like a football. if you're orthodox, do uppercuts while using your left hand as a "punch mit" to stop your momentum. Do the same with your left arm but mimick a left hook (and left uppercut) while using your right hand as the punch mit. You can also lay on your back and chect pass it into the air to yourself. Pass it as high as you can make it go.

if you can get your hands on a ruber one, you can do these against a brick wall. I do them and I also slam an 8pounder against a brick wall for left/rt body shots. Long story short, do these any way you can against a wall while mimicking a punch as closely as possible. With the leather ball, you're a bit more limited but you can still do high intensity rotational motions and the ones I described above.

http://www.rossboxing.com/medballpunch.wmv