They had a Mindbender on the Dom and Jane Show about this very subject recently:
Mindbender 8/12/11
Experts say the best ones last 3.4 seconds...
Answer: A handshake!
They figured that was about 3 pumps up and down, with a firm hand-grip. Any less and you look wishy-washy or insecure; any more and you appear clingy or domineering.
"Now, more than ever, the illusions of division threaten our very existence. We all know the truth: more connects us than separates us. But in times of crisis the wise build bridges, while the foolish build barriers. We must find a way to look after one another as if we were one single tribe.” -King T'Challa, Black Panther
The truth is incontrovertible. Malice may attack it. ignorance may deride it, but in the end, there it is. ~Winston Churchill