Arguments are something I've learned to avoid because I tend to be the one who ends up being lost for words and feeling both frustrated and humiliated. In general you should avoid arguing because even if you win the argument the person you've humiliated will make you his or her enemy. But then there are some occasions where you should argue. I don't think arguing is about being able to come up with something to say on the spot. Its more about memorising a script and recalling the correct line when you find yourself put on the spot. But how to learn this magic script?