rule of thumb.
never discipline a child with a reed that is wider than your thumb
never strike a child in anger
make it a big deal and explain why the punishment is taking place
usually it is "Because you lied to your mother."
always do it in private, never in front of their brothers and sisters.
explain to them that now the punishment has been exacted, as far as you are concerned, it's a done deal never to be brought up again, and they are just as pure as the winter snow. And don't rejoin the family until the child says, "I'm sorry" and you say "I love you."