We use to have him fold his arms. That lasted about a day, I didn't want him to feel like he's always in trouble when we tell him to fold his arms for prayer.
We then switched to putting his hands on his head. So we'll have him stand up against something (wall, couch, cabinet etc.) and put his hands on his head. We leave him there for around a minute (if that) and have him say sorry and explain why he was in time out.
I feel like even though he is only 18 months old he understands. My proof... after he gets out of time out he will go and do that thing that he was just in time out for and then put himself in time out.
Aye aye aye, do any of you have time out success methods? I'm not quite sure he is really getting it...