The tuxedo has been a staple in men's fashion since the late 1800s, when it was introduced as a dinner jacket. There are several accessories which complement the tuxedo, such as the cummerbund. Though there are no hard and fast rules for men's fashion, there are some guidelines for when to wear a cummerbund and which type to wear.
Research the occasion. Formal dinner parties have different dress requirements than weddings, and the rules of fashion tend to change around major holidays. Certain colors of cummerbunds are reserved for Christmas.
Consider the time of day. If you're attending a function before five p.m., you may be required to wear morning dress. In this case, you would forgo the cummerbund for a waistcoat.
Choose an appropriate-color cummerbund. Simple, solid colors are the most elegant and safest bet. Many fashionistas reserve the red cummerbund for Christmas. For weddings, you can choose a color that complements your tie or handkerchief. A good rule of thumb in men's fashion is to wear black if you're unsure.
Wear trousers with a high waist that will be completely covered by the cummerbund. The cummerbund provides a transition between shirt and waist. It is considered tacky to have an exposed waistband while wearing a cummerbund.
Attach the cummerbund snugly around your middle with the pleats facing up. This gives a somewhat slimming effect. The reason the pleats face up is a hold-over from late Victorian England, when gentlemen would tuck theater ticket stubs into the pleats of their cummerbunds.