In an era when an evening suit can be anything from a J.Crew Ludlow worn with Jack Purcells to a broad-lapeled statement piece, it's refreshing to know that there are options that look both casual and elegant.

"Mixing more casual elements into evening is an interesting and inwardly comfortable approach," says Billy Reid, the Alabama-based American designer who won the Council of Fashion Designers of America's coveted Menswear Designer of the Year Award in 2012. "A knit – like a turtleneck or even a striped crew – takes the edge off [a day look] and can look chic when done right. A more casual shirt, if appropriate with no tie, can be nice as well." 

Even a simple white shirt with no tie paired with a great fitting suit can work to stunning effect provided you follow Reid's one hard-and-fast rule: When standing, always, always button that jacket. Aside from wearing a suit vest, there's no quicker way to instantly create a more slimmed-down silhouette.