Spanking is definitely not an effective parenting method. When you hurt a child (even if it's just a spank or 2) the child will eventually be afraid of you... and what happens if someone hurts you and you're afraid of them??? You hate that person right? Most likely, the child will eventually hate you because spanking hurts.
You don't want your child to be afraid of you, you want them to respect you. In order to gain respect, discipline needs to be a learning experience. If a child does something wrong, spanking doesn't teach them why it was wrong and chances are they will repeat whatever the did again. Instead of spanking, timeouts work very well and so does taking away tv and/or computer privileges. If you put the child in time out, when the time is complete, ask them to tell you why whatever they did was wrong and why they will never do it again.