What is the best way to handle two Children when they misbehave at a restaurant? Please Help!!!!!?

I have two children of my own and I was just wondering what is the best way to handle misbehaviour at a restaurant. This is what happens everytime we go out for a nice meal my kids always fight over who sits where and there are always tantrums tantrums. I really need help with this situation so if anyone has any suggestions please tell me