Although this video clip involves defence with a gun it has some very important lessons and is relevant for a non-weapon threat environments:
Being aware of your surroundings at all times and the threats
Don't get blocked, have an escape route
React quickly to resolve a conflict before it starts i.e get the hell out of there
If physical threat is absolutely about to happen react with shock and awe
When the threat is over and you have used approriate defensive force don't keep going as you will be breaking the law!