Think of your dress shirt as your bulletproof vest. It’s the first thing you put on and your last line of defense. When you button it up in the morning, you should feel confident, in control, even invincible. Seriously, putting on a crisp, clean shirt that fits perfectly makes you feel like you're the boss.

But here's the thing: A dress shirt is not any old shirt—there are a lot of details to get right, from the collar to the cuffs to the cut of the torso.

All that said, buying the right dress shirt isn't quantum physics. You can find it at your local mall just as surely as at the fanciest, priciest, most fashionable store on Madison Avenue. You just have to understand the following principles.

Use your head- check your neck: Some guys just buy their shirts in small, medium, or large. No wonder they don't fit so well. You should know your measurements—neck size and arm length—and not just for the sake of it. These numbers are the key to making you look better.

If your collar is so loose it hangs off your neck, or so tight it makes your face blush, you're stuck with it. So take action—get measured. Make sure you can comfortably fit one finger between the collar and your neck. If two fingers fit, the collar's too big.

Trim the shirt fat: You see them everywhere, guys with ballooning dress shirts so blousy they could hide a backpack under them. No matter what your shape, buy a shirt that closely fits your torso. Billowy folds don't disguise; they only amplify. No need for all that extra fabric.

When you head to the store, ask for a slim-fit dress shirt. Everyone makes them these days, even Brooks Brothers. But understand that one label's slim-fit is different from another's. For instance, a Banana Republic slim-fit will be roomier than one by a high-fashion label like Dolce & Gabbana or Dsquared2.

The shoulder seams should hug your own shoulders. Make sure the sleeves aren't too long or too short. When unbuttoned, the cuffs should reach just past your wrists. Whether you're ripped like Taylor Lautner or built like an ordinary mortal, wear a shirt that speaks to your body.

How one tall, lanky dude finally got it: "If you're a tall guy like me (I'm talking six feet six), you know the deal: Nearly everything you try on is too damn small. I make extra-large Band of Outsiders look like its cut for extra-large toddlers. Tall dudes! There's this thing called slim-fit— and even extra-slim-fit.

There are a zillion collars. Ignore them: The spread. The cutaway. The super-duper mega-point. Yeah, we get confused by collar choices, too. But really, you only need to know one: the semispread. It's not too fashion-forward, not too conservative. It works with every kind of suit, every kind of tie. You can't go wrong.

The Style Guy: Nothing looks dressier or richer than a crisp, immaculate, high-thread-count, perfectly fit white shirt or a dark suit. You can always supply color with a tie or cuff links, but that white makes you look brilliant. And white won't clash with anything else you put on.

My grandmother insisted that a gentleman wears white shirts at night (if he has time to change), and she had a point. My favorite is a placket-front French-cuff shirt from Charvet. It works with a tie, but take away the tie and you have a perfectly smooth and clean look. It also doubles nicely with a tux and eliminates the need for studs.

Male-Pattern Boldness: Wear a dress shirt that stands on its own. Now that you understand the fundamentals of how a shirt should fit, you can start getting creative and playing with patterns. Right now we're big into gingham and plaid dress shirts. They add instant punch to your work wardrobe while remaining classic at heart. In the fall and winter months, we prefer richer, more muted tones—the kind that go great with a dark business suit and strike a smart, urbane note. And when the temperature rises, your color palette should, too. Have some fun and reach for a lime green, pink, or lavender gingham. Live a little.

Surefire Tip: Real Men Wear Pink. "We've been putting the pink shirt in the magazine for years now, because we really believe that it's as much a staple as the white dress shirt. Guys might think, 'Oh, I can't wear pink,' but it all depends on what kind of pink you wear. You don't want a bubble-gum hot pink; you want a light pink that's more a pale shade of rose. Wear it with a simple dark tie and that color flatters everyone's skin.

It's All in the Wrist: In praise of the unbuttoned cuff. How you wear your shirt can be as defining as the shirt itself. This may mean leaving the collar of your oxford unbuttoned (as so many well-dressed Italian businessmen like to do). Or it may mean doing something as seemingly insignificant as leaving your cuffs undone. It says, "I'm not some buttoned-down middle-management lackey" (or at least that's what we like to tell ourselves).

Really, it makes you feel more relaxed while still looking sharp. Of course, it needs to be done correctly. The sleeves of your shirt should fit just right— the cuffs should hit the hinges of your wrists so they poke out about half an inch past the sleeves of your jacket. If they run halfway down your thumbs when unbuttoned, you'll look like a little kid wearing one of his father's dress shirts. And no offense to Dad, but that's not the look you want.

Style Police: Go Tuck Yourself. Okay, here's the deal. Letting your dress shirt hang out doesn't make you look younger or thinner. It makes you look like you're wearing a muumuu. Traditional dress shirts aren't meant to be untucked; they're cut long so they remain in your pants. Tucking in your shirt won't kill you; it'll just make you look better.

Ditch the one off your back and upgrade with our essential guide: how to make it fit, inject some color, and keep it all looking crisp and clean.