Edge up; cut, don’t stab. Don’t forget you have two hands and two feet—the blade is a distraction as much as a final argument. In the first instance, threaten the face. In extremis: think of it as a cat’s claw, and use it to open the seams of a striking arm as your attacker tries to withdraw. If you get drawn in close, take it to the inner thigh and twist, but for preference: don’t, because the other fellow is likely heavier and stronger and hard men do so love to throw their weight about.