Obviously I haven't got to the parenthood stage yet but I'll give my opinion on this matter anyway.
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It's definately not a black and white issue. It's definately not "don't spank your kids ever" and "spank your kids whenever possible". A 'mix' is good. What I mean by this is doing it when necessary. But knowing the time to do it and the time not to do it is the hard part.
Let's say that your kid is messing up. A firm "don't do it" or "that's wrong" or whatever should be fine if it's the first few times they're doing it and/or they're young. But it it's a repetitive thing, then gradually build up the 'punishment'. Grounding is good. A smack/spank can be effective, but definately resort to other measures first, as it can frighten the kids. And when spanking a child, them knowing that it's been done for good and in a loving matter (which is how it should be done) is important, otherwise they might get scared and think they're being abused, but hopefully they know you well enough to know that you wouldn't do that to them.
I think I've lost myself along the way, but my summary is this:
Resort to other measures first, and do it in a loving matter. Keep in mind the severity of the thing the child did wrong and how many times they've done it. The age of the child is also important.
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I just had another thought - the motive that the child did the 'wrongdoing' is important. Also, I think after the 'incident' it is important to sit down with your child to talk it through with them.
Just my
