Whenever the kids come round to mine, they are all told of certain rules of the house - no running, leave the cats alone, no throwing, no one out into the garden etc and they generally are very good with this (especially little Nathan who takes great delight in telling his older siblings what they can and can not do). On the occassion when the tantrums, sulking and nortyness arise a firm voice and look followed by "no that's not what we do" or "nooooooo!" (whilst grabbing hold of the little blighter in mid throw/run/hit) and a gentle explaination of the wrong doing usually works altho of course does not always work. In such situations the norty step, threats to b taken home and "if you're going to be norty we won't play with the water/cars/buy you a pressie etc" ensue. Luckily my lot are all under the age of 8 so rules are easier to instill... I'm beginning to dread the thought of their visits as they get older tho :-S