1. The mod look requires commitment—you can't half-ass it—so start with a foundation suit.This one from Dior Homme should be your guide: It's cut slim, with a shorter jacket and pants cropped at the ankle (trust us, it's best to buy one that fits the bill rather than have something from your closet tailored).

From left: Runway looks from Dior, Gucci, Lanvin.

2. There are plenty of hallmarks to this style, but few are as iconic and of-the-moment as a well-made pair of Chelsea boots. Although you can find countless elegant versions out there, we're partial to Saint Laurent's suede iteration.

3. In their heyday, mod guys wore parkas to keep their clothes clean while riding Vespas. This season, designers have embraced boxy, textured overcoats, but the proportions remain the same—choose a structured top layer with lots of volume (like Jamie Hince, pictured below, left) to contrast with slim pants.

4. Don't forget about grooming. Go clean-shaven and opt for a short haircut with piecey, tousled bangs. Think effortless, but not full-Beatles mop top.

5. Once you know the rules, it's okay to break them (a little). Try switching out suit pants for dark-wash denim—like Justin Theroux in the photo below (right). And steer clear of any embellishments. Pleats, pocket squares, and piping have no place here.

*This article also appeared on Details