Instructions
Assess the situation of the cat. If training the cat or if the cat is behaving aggressively, only then should you pick up the cat by the scruff.
Grab the scruff of the neck as gently as possible with one hand.
Lift the cat off the ground only 4 to 5 inches. Any higher will put undue pressure on the cat's skin.
Keep the cat off the ground for about six seconds. This short amount of time is enough to gets the cat's attention and stop the unwanted behavior.
Put the cat gently back on the ground.
How to Pick up Cats by the Scruff
Mother cats pick up their kittens by the scruff of the neck. The scruff is the loose skin at the back of neck. Holding a kitten in this way does not hurt the animal, but picking up a cat or kitten in this manner shows dominance. When a cat is picked up this way his body goes limp, showing submission. It is best if human owners don't pick up adult cats by the scruff. This may cause stress on the skin, which holds the entire weight of the cat. But if a cat is misbehaving or fighting or engaged in other aggressive actions, picking a cat up by the scruff stops the behavior immediately.