The main thing that you need to remember is that black tie is intended exclusively for social occasions, never business. It should not be thought of as simply a more formal version of a business suit, although many retailers seem to construct tuxedos in this way, perhaps in an effort to save costs by designing fewer patterns.

Many commonly seen deviations from traditional black tie bring the tuxedo closer to the business suit. While not distasteful or inappropriate, these deviations may decrease the elegance of the tuxedo in the eyes of some because they represent the carrying of the boardroom into the ballroom. These include long ties, vented jackets, single-breasted jackets with more than one button, notch lapels, and cap-toe shoes. Again, these are not “wrong”. These days, few enough people know what classic black tie looks like that most will not even notice. If you have a tuxedo with a notch lapel, there’s no reason to burn it. This is just to give you a better idea of the spirit of the thing.

Finally, a word about “creative black tie”. Every year at awards shows we see celebrities eager to show how clever they are by breaking the rules of black tie in unexpected ways. They usually look terrible at the time and even worse as time passes and we look back at the photographs. At this point, you can make a stylish, while at the same time elegantly unobtrusive, statement by wearing a classically styled black tie outfit. It shows respect to your hosts who created the black tie affair, and allows you to enjoy the atmosphere of the evening without wondering whether everyone is gawking over your “creative” outfit out of jealousy or repulsion.

The “rules” of black tie are well laid out on blacktieguide.com, a site devoted exclusively to this purpose. The Put This On - Black Tie article gives Cliff’s Notes. The Styleforum threads offer discussion of the meaning and purpose of black tie, as well as historical precedent for and elegance of various deviations from standard black tie.

Further Reading

The Basics of Wedding Attire

The State of Black Tie Your Observations

Blacktiefoo Shirt Studs and Other Fooish Contemplations