If a man's wardrobe is his arsenal, suits are the heavy artillery. They can make a businessman into a boardroom general and a bookish type into commanding presence. Still, most men's suits spend most of their time in the closet, waiting to be rolled out only for special occasions. According to designer Todd Snyder, this is a strategic mistake.

Snyder is a big fan of using suits and suit separates for off-duty dressing, especially for dates: "Women want to know that you are versatile." But, in order to make a more casual look work, you'll have to have the right sort of suit. "Tailoring is a must," Snyder explains. "Most suits can be dressed down but they need to be the right fit. Double-breasted suits are hard to dress down unless you live in Miami or Milan."

Snyder insists on the "Rule of Two": When dressing down a suit, never change more than two elements of the look. For instance, you can swap out the pants for some dark jeans and lose the tie, but keep the leather dress shoes. Or if you want to wear sneakers with dark jeans under your suit jacket, keep the tie in place to balance out the casualness of the rest of the look. When all else fails, Snyder advices men to wear an expensive watch, which can make up for missteps elsewhere.

Throwing sneakers into the mix is a popular way to dress down a suit, but the approach is not without its pitfalls. We asked the sneaker pros behind the up-and-coming shoe juggernaut GREATS brand to weigh in. A sneaker can be a great complement to grey, navy or khaki suits, says GREATS co-founder John Buscemi, but never, ever with a black suit. "It's just wrong. Never wear sneakers with black suits at all actually." Something about black simply doesn't work with the sporty casualness a sneaker inherently implies. A low-profile, sleek, clean leather or canvas sneaker can make a great contrast against a suit. Converse Jack Purcell's are a classic choice, but it can also make sense to invest in something a little more luxe, like kicks from Margiela or Common Projects.