Here are my thoughts.
The Bible is clear when it provides us with direction about children.
First of all Jesus let's us know his feelings about children in these scriptures.
"Whoever receives one of these little children in My name receives Me; and whoever receives Me, receives not Me but Him who sent Me." (Mark 9:37); "Assuredly, I say to you, whoever does not receive the kingdom of God as a little child will by no means enter it." (Mark 10:15)
These scriptures tell us that Jesus has placed high importance on children and their place in the kingdom. There fore it is safe to say that their wellbeing is of utmost importance to Him.
He later gives us guidelines to follow with regards to rearing them. He says that we should train up a child in the way he should go and that if we spare the rod we will spoil the child. It is clear that He intends for us to find a balance between the two. Neither of these methods is independent of the other.
I believe that if you take the time to train your children properly, then spanking them will only need to be done sparingly. My rule of thumb was to use spanking only when the offense would result in physical harm to the children or to others.
Furthermore, extension cords, broom handles, and such go far beyond spanking. They are abusive.
What do you think?