I have a son - 7 years old and i have never spanked him - never will.
There's absolutely NO need to.
I was spanked as a child and it's painful - humiliating and mostly done out of my parents anger/frustration and i deeply resented it.
If your spanking your kid YOU need to look at yourself and ask yourself what the fuck are you getting to that level of anger and frustration for - what you could do different etc.
You can take away treats / TV/ computer etc - SO many options as an alternate form of punishment...
Also try REALLY talking to your kid on their level - get down to their height - eye to eye and really talk to them so they hear.