Rule No. 6:
While it feels as effortless and comfortable as a T-shirt, a lightweight knit (be it silk or a wool-cotton blend) is amazingly breathable and makes a suit jacket look eminently sharper (below).

Lightweight knits, from top: Ermenegildo Zegna Couture ($590). Brioni ($750). Gucci ($640).

On models, from left: Suit ($1,990) by Valentino, Shirt ($300) by Christophe Lemaire, Shoes ($75) by Adidas Originals. Jacket ($920) by Officine Generale, Shirt ($75) by Rag & Bone, Pants ($495) by Boglioli, Shoes ($735) by Gucci.

Rule No. 7:
Suit separates aren't meant only for the nine-to-five grind. A lightweight, unlined blazer with a soft shoulder (above, left) and matching pants can be just as comfortable as khakis and a denim jacket.

Rule No. 8:
Even the most familiar patterns can be smartened up by way of unexpected tweaks to the color palette. In the case of the M65 camo zip-up, the tones are darker, lending a grown-up, sophisticated vibe that your old army jacket can't match.

Rules 9–12 →