The most important thing about disciplining a child is that the child should understand that discipline is about the behavior, not the person. The child should come away from it thinking, "THAT is something I don't want to do again," rather than, "I'm a bad person." Abusive punishment tends to make the child think that they are bad and undeserving of love, rather than thinking that they are loved but did a bad thing. The reason corporal punishment is frowned upon is that it is very difficult for a child to comprehend that vital distinction when someone is busily hitting on them.

That doesn't mean it's impossible. If a child is old enough, you can sit them down and explain what's about to happen and why. (If s/he's not old enough to understand an explanation, any form of corporal punishment is abuse - you don't spank babies.) There are still caveats:

>you need to deliver it calmly or they see you as having lost control, which communicates to them that it's OK to lose control. Wrong message to send to a child. Way wrong.

>The Constitution's prohibition against cruel and unusual punishments applies to you - not legally, but pragmatically.

>however you do it, you end up communicating that it's OK to do violence to another person under certain circumstances. That's not a good message to send either, but other avenues will tend to teach them to restrain that impulse, so it's not a terribly big problem. Still, don't be terribly surprised if your high-schooler gets himself into trouble for punching out the jerk who played a dirty trick on him.

All that being said, corporal punishment even at its best is an inferior form of discipline. That's been borne out in various studies. The single most effective form of discipline is one that has consequences that relate logically to the act itself - mostly because that kind of consequence is the easiest for the young mind to understand.

By that, I mean if you make a mess, your punishment is to clean the mess you made. If you break something, you have to pay for the replacement - even to giving up something of your own or doing odd jobs to earn the money to do so. If you hit or fight, you stand in the corner away from people with nothing to do but reflect on how truly boring it is being alone while everyone else is having fun. If you lie, or cheat, or fail in basic responsibilities, then you lose some of the privileges accorded honest, trustworthy folk - you have an earlier curfew, endure the embarrassment of having your parents call to check up on you when you're at a friend's house, or lose the right to leave the house without parental escort. Some logical consequences are less clearly linked but no less effective: an early bed time on the argument that someone who did THAT is clearly too tired to think straight.

It's also useful to make it clear that the extras they enjoy -television time, video games, etc. - do not come free but are the rewards of good behavior, and that they can be withdrawn when good behavior is absent. This is best used for encouraging desired behavior - keep your room clean, obey your teacher in school, etc. - rather than eliminating bad behavior.