Is there an age when you begin to spank?
There is no excuse for spanking babies or children younger than fifteen to eighteen months of age. Even shaking an infant can cause brain damage and death at that delicate age! But midway through the second year (eighteen months), boys and girls become capable of knowing what you're telling them to do or not do. They can then very gently be held responsible for how they behave. Suppose a child is reaching for an electric socket or something that will hurt him. You say, "No!" but he just looks at you and continues reaching toward it. You can see the mischievous smile on his face as he thinks, I'm going to do it anyway! I'd encourage you to speak firmly so that he knows he is pushing past the limits. If he persists, slap his fingers just enough to sting. A small amount of pain goes a long way at that age and begins to introduce children to realities of the physical world and the importance of listening to what you say.
Through the next eighteen months, you gradually establish yourself as the benevolent boss who means what you say and says what you mean. Contrary to what you have read in popular literature, this firm but loving approach to child rearing will not harm a toddler or make him violent. To the contrary, it is most likely to produce a healthy, confident child.