N.M.
Hi J.,
I just wanted to add my voice to the chorus of "be consistent". I have a 25 month old daughter and when she pushes or shoves one of her friends, she has a time-out away from the action and when the time-out is over, she has to come back and tell her friend "I'm sorry for pushing you". We've been using time-out since she began having play-dates at 18 months and it took awhile for her to really "get it" but she does get it now and she rarely exhibits negative behaviors anymore. (I think her last time out was over three weeks ago.)
I don't agree with the idea of swatting/spanking/tapping/patting children to teach them that hitting is wrong... I believe that if they get hit, they will be more likely to hit.
Good luck.
N.