I try to be zen about it. It's just how kids communicate when they're upset or really want something. It's often just an expression of their need for attention, or maybe they're tired or hungry and not coping well themselves. We do the same as adults, it's just that we aren't so dependent on the attention and responsiveness of the adults around us so don't tend to irritate each other quite so much
I try not to punish or criticise the behaviour, as they can't stop it and they're not trying to be annoying or difficult, it's just the way they feel. It is hard at times, particularly when I'm really tired! I do lose my temper at times. I try to take myself away for a breather if I can.