Quoting CottonCandyKiller:" do you think is appropriate for time outs? obviously i have a while to worry about it but i'm just curious what other mom's think. i know it depends on the kid but on average?"
We started around two. They say to use it for one minute for every year of age. Of course it's best to also explain to them why they are being put in time out. It was much more effective when my son was little because he hated not being in the same room with us, and now he doesn't really care as much :/ .