Perhaps the most common mistake is wearing the cummerbund upside down. That would be with the pleats facing down. The pleats of a cummerbund should always face up. There are various stories as to why the cummerbund was created and these stories illuminate why the pleats go up.
One is that men’s formal trousers in the 19th century did not have pockets and the gentlemen used the cummerbund to hold their theatre tickets. Another story says that the device was designed to catch crumbs at formal dinners, keeping them off the trousers. Whatever the case may be, if you remember either story your cummerbund will always face up like your smile.
Another mistake you definitely don’t want to make is wearing anything but black formal shoes with your black tux. Brown, white or any other color with black tie is deadly, If you’re trying to be a rebel, wearing the wrong shoes is not the way to go. Your shoes should be polished and look impeccable.
White socks are also a no-no. In some ways, you’re better off wearing no socks at all. That says rebel—you’re breaking the rules—but white socks signal that you have no idea what you’re doing.
One thing to remember before you decide to break any rules is that you should first know the rules. If you’re going to go against the grain when attired in men’s formal wear, you should do so with full knowledge of what you are doing and why you are doing it.