Once upon a time, dressing like an adult was dead simple -- and totally boring. If you wanted to be taken seriously as a professional you showed up in a nice suit with a classy briefcase or handbag. Daring to be creative meant a colorful tie or a bright accessory. And that was that.

These days, however, you're just as likely to spot your local billionaire in a hoodie as in an bespoke Italian suit, or catch a CEO dressed in her biking gear as see her rocking a pencil skirt and heels. Few of us miss the rigid old ways of dressing, but the new wardrobe free-for-all can be confusing.

If a suit is just going to make you look stuffy and out of touch, how do you signal you've arrived at actual, successful adulthood? If creativity is encouraged, how do you exercise yours without stepping over the line and becoming the talk of the office for all the wrong reasons?

Two recent articles, one from Vanessa Friedman in the New York Times Fashion & Style section, and another on blog Science of Us highlighting recent remarks by Project Runway mentor and all-around fashion icon Tim Gunn offer all the wisdom you need to dress like a fully fledged adult in a world full of hoodies.

1. Own it.

For certain serious types, worrying about your clothes can seem kind of frivolous. Others write themselves off as "not the fashion type." But even if you're out to change the world or far from a lifelong Vogue subscriber, you still need to pay attention to what you wear. If you're an adult, fashion is not beneath (or above) you.

"I believe in the power and appropriateness of semiotics," Gunn said at the James Beard Foundation Food Conference in New York. (If you're a few years away from your last college literature class, semiotics is the study of symbols). "The clothes we wear, the accessories we wear, the way we groom ourselves sends a message about how we want the world to perceive us. It's a very important responsibility and we need to accept that. I don't care how people [do it], as long as they own it."

In other words, you can wear nothing but grey T-shirts like Mark Zuckerberg if that's your thing, but you have to think about why you're doing it and make a conscious effort to consider how your clothes make you -- and others -- feel.

Another part of owning it, Friedman insists in her article, is simply taking care of your clothes. Learn to iron and sew a button, and for the love of all that's holy, stop leaving laundry in a heap on your floor. "Well-kept clothes suggest clothes that are valued, which suggests clothes that have been earned -- which suggests independence. And that suggests adulthood," she says.

2. Don't distract.

This essential bit of wisdom also comes from Friedman. "Clothes should not be the focus of attention, which is to say, they should not be what colleagues or friends remember after a meeting," she writes.

That means you should wear garments that require no distracting fiddling and cover up enough that people will recall your professional contributions rather than your, ahem, other attributes. "The point is: You want people around you to think about what you say, not what your clothes say. They should support performance, but not be a performance," she concludes.

3. It's OK to wear a costume.

When we're younger, we generally strive to find clothes that make us feel comfortable -- that express our true selves -- but when you get older, you should aim for another target, according to Friedman. Dress not for who you are, but who you want to be. Not because you're out to trick others, but because you will trick yourself. Clothes can be a surprisingly effective tool of self-transformative, she believes.

"Part of dressing like an adult is dressing in a way that distinguishes your grown-up self from your adolescent self," she claims. "To a certain extent, this means playacting at adulthood until your inside catches up with your outside... It means that if you see a garment and think 'costume,' that doesn't mean you should avoid said garment; it may even mean you should buy it. It will start to feel natural soon enough."

Would you add any other rules to this list?