The Trouser
Traditionally, a black tuxedo trouser will match your jacket, and will have a grosgrain stripe down the outer side of each leg, to tie in with the jacket lapel. However, if you’re going for a statement jacket, revert back to black, as coloured trousers aren’t a good look.
Pleats or flat-front
Front pleats are making a comeback, providing a traditional point-of-interest for those wanting to stand out. However, be warned with pleats: the extra ruffles at the front best suit leaner, taller gents due to the extra volume they provide.
Slim or Skinny
As for the fit, stick with a slim or straight cut, depending on your body type. But avoid a skinny fit. You want to ooze elegance at the ball, not use it as an opportunity to boost your streetwear cred. For the perfect fit, have your suit personally tailored to your size.
The waist should fit snug with no bunching or pulling, and ensure you nail the trouser break, where the hem kisses the ankle before the shoe. Style mavens can opt for a slight crop at the ankle (nothing crazy short though) and a chunkier hem for extra fashion points. Otherwise, stick with a traditional pant hem and leg length.
Above all, your tuxedo fit, both jacket and trouser, will literally make or break your black tie look. So invest in getting measured up and sized before anything else.
See also: Gentlemen's Guide: 5 Ways To Spot A Quality Tailored Suit