Agreed with no rough housing. I have a pair of sisters who want to do it ALL the time. I tell them they can do it at their house, but not here. There are days I feel like the "fun police" no, no no... :P I also allow the arguing for a short while to assess the situation. If it escalates I step in, otherwise I allow them to learn how to solve the problem or assist in solving the problem (does it really matter if you both have green plates? - maybe we should switch them- or how about no plates?). I often like reversing the tables too if they are fighting over who has a bigger piece of food (as an example- can do this with toys too). Ask one of the kiddies to cut the piece of food. They naturally think they will get to select their piece too and will not necessarily cut it equally. However ask the other child to choose a piece first. Quick lesson learned on being fair I have watched many faces turn to shock and then I take the time to explain why it is important to be fair.