Lol @ mb
We haven't started. She wouldn't understand and there is no way I am putting her in the crib for punishment (it seems like so many people do that).
We started it a few weeks ago. I put DS in a corner and stand very close to him so he can't run away. He usually cries so bad that standing is optional. I only do this for biting and repeated hitting. He's only in the corner for 30 seconds-1.5 minutes. If you are looking for suggestions on a time frame, use one minute per year of age (goes with attention span).
I have been trying it with ds, but he doesn't get it. He sits on the step when he knows he did something wrong (usually throwing his sippy cup or toys), but he just giggles and says "nononono"! because that is what I say.
It's kind of funny but I do my serious face and he still laughs.