Breaking out of age-based style clichés can add impact to any man's image. But it's dangerously simple to slip up when you're trying to stand out from the generational herd. Wearing a three-button pinstriped suit at the age of 25 can look like posturing; throwing on a backward baseball cap at 42 can come off as overcompensation. What's the key? Developing a deeper style, a more refined clothing palette, and a desire to simply dress better and beyond your years without violating certain cardinal rules. These rules mutate slightly from your 20s through your 40s, so we've laid out this guide to dressing by the decade.

20s
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WEAR THIS: a tailored jacket Smart clothing can help propel you toward a career goal; slouchy looks can trip you up on the first few rungs of the ladder. The jacket is your go-to tool. It lets people know you're serious--about that promotion, that girl, or that girl's parents. In your 20s, begin building a closetful of carefully selected blazers and you're off to a solid sartorial start.

NOT THAT: trends that don't work for your body type If you have the thighs of a thoroughbred because of all the soccer you played in college, avoid skinny jeans or you'll look like a stuffed sausage.

The Rising Star

INC International Concepts blazer ($170), (800) 289-6229; Vince shirt ($175), available at Barneys; Monogram Collection by Banana Republic tie ($70), bananarepublic.com; DKNY Jeans jeans ($60), (800) 777-4524; Tretorn sneakers ($75), (866) 485-5946

30s

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WEAR THIS: better shoes Shoes are the easiest way to determine whether a guy is playing in the big leagues or just fronting. Suits can be difficult to gauge, but it's pretty easy to tell the difference between a $700 pair of cordovan wing tips and a $50 pair of black rubber-soled, square-toed lace-ups. And which one do you think says "my career is going swell"? Think of your shoes as investments, and treat those kicks as well as you would your car--meaning regular checkups and polishing.

NOT THAT: heavily logoed T-shirts from companies that actively target high-school and college students Actually, skip all shirts with logos, or at least choose something with demure brand placement. It looks bad to shill for someone else, and if you're standing in a bar next to a 21-year-old wearing the same T-shirt, you'll look like his unemployed uncle.

The Heir Apparent

Perry Ellis suit jacket ($350), suit pants ($150), and shirt ($70), perryellis.com; Luigi Borrelli belt ($650), https://dimepiecela.com; John Lobb shoes ($1,030) (212) 888-9797

40s
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WEAR THIS: a trademark At this point, you should have mastered jackets, suits, and shoes. Now your challenge is to show laid-back leadership: You've risen comfortably above the fray, but you're anything but retired. Find an accessory you love and then stock up. Maybe it's cuff links. Swiss watches. Cashmere socks. Pocket squares. Choose one thing that helps you stand out, so you don't disappear in the crowd.

NOT THAT: rips, tears, or worn fabrics Sometimes a frayed edge comes into style. Sometimes modern jeans have a lot of fading. A 20-year-old can pull that off, but you'll look like Nick Nolte.

The Casual Kingpin

INC International Concepts cardigan ($70), (800) 289-6229; Perry Ellis shirt ($80), perryellis.com; Rag & Bone trousers ($235), www.denimbaronline.com; Converse sneakers ($60), converse.com