I do head-banging (not for a while though) and biting. My wrist has three bite scars. One is my own, the next from my guanaco, and the other one is just a mosquito bite that I keep picking at.

There's a difference for me between the head-banging and biting vs. cutting. Cutting has more thought behind it. It's sometimes planned (at least for a few minutes), and I can delay it. The others just happen in a moment when anger is particularly intense.

I think that the best way to deal with it is to remind yourself that those feelings are momentary, and will go away. Train yourself to use deep breathing or relaxation techniques to get through it. Once you get through the intense emotions, doesn't the desire to hit or bite tend to fade away?