Originally Posted by Judokas
For fists look into the conditioning of traditional Karate they have great conditioning.
Also if you use gloves...hit the bag with gloves and every once and a while take off the gloves and punch bare handed until your hands start to hurt then go back to gloves etc.
The gloves don't supply the same effect. You want them to harden at first, or at least that's what worked for me. If you slowly do it, you could build "just enough" damage. The initial damage was good for me. maybe I'm different..
Also, at first, don't hit as hard as you can. Start with like 25 %, then 75, then 50, then 75, or so. Never punch as hard as you can unless it's in a fight.