Yup I agree with the other ladies ~ consistent and clear expectations that is not acceptable behavior, role modeling of socially acceptable alternatives and language they can learn to use both in the moment to resolve the conflict and during 'other times' of the day just practicing how to play properly.
I personally do not make children say 'sorry' because IME it just becomes a word that means nothing ~ in centre care what I saw when this was regular practice after poor behavior to say 'sorry' was that children just started to think I can behave however I want as long as I say SORRY and it would often take on that 'tone' of them not truly meaning it at all you know that SoREEEEEEEE
For me actions speak louder than words ~ I want them to SHOW ME they have learned their lesson on not to do this so what I prompt is 'Wow that really hurt Sally ~ what do you think you can do to help Sally feel better about what just happened' and see what they decide to do make amends and make sure they check with Sally that it WILL make amends ~ some will give a hug, or say sorry or give a high five or let them have a longer with the turn the toy they were fighting over and as they get older they will add 'I will try harder to use my words next time instead of hitting so I do not hurt Sally in the first place' and so forth ... to truly learn remorse and making amends.
I also love puppets ~ sometimes if I have a child struggling with a social skill I will have two puppets 'misbehave' in play in the manner the child has been misbehaving and talk to the child about 'wow should they be doing that?" 'what else can they do' ... if they are not old enough to TALK I will still play this game but will provide the 'answers' to the questions and walk through behavior modification with the puppets to help the kid SEE /HEAR and thereby practice BETTER conflict resolution skills.