Depends--are we talking about a weakling or someone who could actually do damage here? If it's someone who isn't much of a threat, restrain the person and ask them what their problem is. If it's someone who could hurt me, then attempt to disable them at weak points (i.e., kick to groin, taking out the person's knees and/or elbows, blind them in some way, etc.) before they can do the same to me.
