Not a cheap-looking suit.
It's getting harder and harder to tell whether a man's suit is any good. The arrival of modern cuts and quality fabrics at various "fast fashion" retailers, such as Zara and H&M, mean a suit can look great and fit nicely without being especially well constructed or costly.
But one thing is a dead giveaway of a bad suit: the lapel roll of the jacket.
On a suit jacket of reasonable quality, the lapel will always exhibit a gentle, soft, curling roll from the shoulder and collar line, down the gorge to the point where the jacket buttons. Here's a reasonably good example, starring Chris Hemsworth at the UK premier of the "Age of Ultron" Avengers sequel:
Hemsworth is actually a bit of a tailoring challenge, given that he owns a very sculpted, top-heavy physique that's really not ideal for outfitting in a suit jacket (guys with bulky upper bodies are always going to stretch and pucker the jacket in unusual ways, but if the cut is too generous, the proportion between jacket and trousers gets messed up). He looks great in the "Thor" costume. But he also looks pretty good in this Calvin Klein Collection suit, though the jacket does pucker ever so slightly more than it should at the buttons (it should, in fact, pinch not at all when buttoned).
Still, you can clearly see the roll, something Calvin Klein suits get right, interestingly, at many different price points, at least in my experience.
Some suit jackets showcase a perfect roll because of the extensive thought that has gone into their construction. Here's former Ferrari chairman Luca di Montezemolo (on the right) standing next to current Fiat Chrysler Automobiles (and current Ferrari chairman) Sergio Marchionne. Montezemolo's suit is most likely bespoke, and the roll of the lapel is exquisite:
But a suit jacket doesn't have to be custom stitched by a tailor to have a good roll. Nor does it have to do be outlandishly expensive. But for the most part, el-cheapo suit jackets have a lapel that doesn't roll, but rather flattens out abruptly just above the first button. This makes the entire lapel area, as well as the front of the jacket, look as if it's uncomfortably or ill-fittingly attached to the wearer. A good roll, by contrast, makes the jacket look fitted to the man and creates a bit of slightly raised dimension, providing the jacket with subtle oomph and depth.
When you're trying on a suit, be sure to check the roll. A thumb should be able to find some room as you slide it under the lapel, moving down from shoulder to button.
The jacket below is not what you want. As you can see, the first button looks as if it's floating in a sea of fabric. Overall, this entire jacket exudes inexpensive, in a bad way as it fits poorly and lacks any critical quality cues, starting with the terrible lapel roll.
Clothes do indeed make the man (or the woman) ... but not in a good way.
A defining feature of a suit jacket is the lapel. It's important that it be done right! It should be one of the first things you examine when buying a new suit — and if the roll isn't right, it should lead you to
try on something else.