We haven't spanked yet because we don't think they'll understand it. I'm hoping we never have to.
We keep away from smacking MIAF's daughter on the butt. More so because she talks about everything, and with a custody battle on the horizon, pre school teachers, etc, we can envision a nightmare on that front. Sad part is, she's a total bastard whenever she comes back from her visitations with dickface on the weekends, because she's so bored there and they just let her run wild.
In lieu of spankings, we have done a number of things. If she doesn't eat dinner, no dessert and no cartoons before bed. Time outs a-plenty. Worse than that, I make a "phone call" to Santa to put her on the bad girls list. If she's worse than that, she comes home to see her room COMPLETELY devoid of just about every toy except maybe one or two.
The funny part is that now, I barely even have to raise my voice. On the rare occasion that she misbehaves or decides to whine or cry, I just give a stern "excuse me," and she shuts up INSTANTLY, lets me say what I need to, makes the proclamation that she wants "to be a good girl now", and is on her merry way.