I always liked Derren Brown’s approach as described here:
Outlining his irrational behaviour strategy in the Metro today, Brown recalled an incident when he was approached by a suspicious character spoiling for a fight on his way home at 3am in the morning.
“I said to him, ‘The wall outside my house isn’t 4ft high’ and he was suddenly confused.”
The idea of the psychological tactic, he added, is a bit like “pulling the rug out from somebody”.
“He started breaking down in tears because all of that adrenaline and aggression had to go somewhere. So he did the adrenaline dump. They use it in martial arts where they get people to relax before you hit them to make the blow more powerful.”
The key, he said, to being prepared is to remember a random line or a song lyric you can use – and the more out of context it is, the better.
“It’s not quite the magic trick, but it will save you a lot of pain and money.”
Of course, if you should ever see Derren Brown approaching you on the street and smiling, the best course of action is to run the fuck away.