What to Wear to Any Party, From Cocktail Attire to Casual

As if figuring out what to wear on an average day weren't hard enough, now you have to decipher what's "casual chic" versus "festive cocktail attire."

"Hosts are getting so creative with dress codes that guests are left scratching their heads," says Derek Guillemette, the former director of ready-to-wear for Rent the Runway. Customers frequently ask the company's personal stylists about which styles will fit well and fit within a certain dress code. And it's not only women—men are stumped, too.

Enter this handy guide to dress codes to ensure you and your other half can rise to any occasion in style.

Black Tie Dress Code

Think formal attire and glamorous details.

Attire for Women:

A tea- or floor-length gown is the way to go for upscale events, like formal weddings, charity galas, fancy holiday parties, and awards ceremonies. Be a celebrity for the night and strut your stuff in a gorgeous satin, taffeta, or beaded number. Try a Hepburn-esque column or an A-line in red, navy, or emerald, which stands out from black and complements many skin tones, Guillemette says.

As for accessories, "choose a dramatic necklace or dangling earrings, but never both," he adds. When in doubt, opt for time-honored classics, like diamond drops or a pearl necklace, over something too costume-y. And an evening bag is a must; invest in one metallic clutch that can look dressed up or down for all your parties.

Finally, be wary of trains and fishtails (no one wants to trip at a black-tie holiday gala), loud prints (rethink that cheetah dress), and body-conscious styles (save them for A Night at the Roxbury). In the South, the rules of black tie attire are strictly adhered to, and decorum prevails, says Tara Guérard, the owner of Soirée, in Charleston, South Carolina, an event planning and design company. Be especially mindful about not spilling out of necklines and slits.

Attire for Men:

A tuxedo with a black bow tie. "Make it a real tie, not a clip-on," Guillemette says. Whether you rent or buy, select a trend-defying notch- or peak-lapel jacket with one or two buttons. The dress code tends to be more lax on the West Coast, where more men are getting away with dark suits.

Cocktail Dress Code

Cocktail attire translates to semiformal. Think elegant party dress and a great pair of heels.

Attire for Women:

"The LBD is your BFF for most weddings and engagement parties and many fund-raisers," says Catherine Loose, the director of fashion for Style-Architects, a styling and event-planning service in Minneapolis. Turn to rich fabrics, such as lace, chiffon, and velvet, to elevate the typical black with texture and dimension. But keep the hemline modest: two inches above the knee max. To test if your hemline is too short, stand with your hands at your sides; the dress shouldn't be higher than your fingertips.

You can branch out to other shades, too: Jewel tones and icy pastels can be just as refined in simple silhouettes. It's also perfectly acceptable to splash out in dressy separates—say, brocade cigarette pants topped with a beaded shell. Whichever you choose, fancy footwear is mandatory. The daintier the high heel, the more graceful your shoes will look on the dance floor (even if you have two left feet).

Attire for Men:

Go for dashing and timeless. "Wear a dark suit that's a well-fitted, toned-down version of a tux. That's what separates it from what you would wear in the boardroom," says Guillemette. "Stick to a white shirt, a dark tie, and black cap-toe oxfords." For the final touch: Give those dress shoes a respectable shine.

Festive Dress Code

Also known as holiday attire, creative cocktail attire, or dress-to-impress. It means to bring the razzle-dazzle.

Attire for Women:

"Color, bold jewelry, and sparkly details show you're ready to have a good time," Guillemette says. You'll often spot this dress code on invitations for holiday parties, but it doesn't mean you have to whip out the jingle-bell earrings. "Go all out with sophisticated bling and a vibrant dress," recommends San Diego lifestyle and etiquette expert Elaine Swann, who says that a jacquard skirt with a silky blouse works, too. Add more glad tidings with statement accents: a bib necklace, red pumps, velvet embellishments, or a glittery clutch. Don't let freezing temperatures put a damper on your fabulousness, says Loose: "In the Midwest, women often layer with a jewel-embellished cardigan, opaque tights, and heeled booties." And you can never go wrong with a statement coat.

Attire for Men:

"Go for a playful vibe with a velvet blazer or a classic suit with a fun tie," says Los Angeles-based stylist Eric Himel. But "fun" doesn't have to mean emblazoned with candy canes; you can also look for holiday-colored stripes or a tartan. Prefer to lose the stuffy Windsor knot? Pair gray flannel trousers with a green cashmere sweater, or try colored corduroys with an open-collar shirt and a tweed sport jacket.

Dressy Resort Dress Code

Dressy resort is synonymous with island chic or garden party, and it's common to see on an outdoor wedding invitation. Think easy and breezy with a touch of elegance.

Attire for Women:

Balance fashion and function. "Slip on a comfortable maxi dress, a flowy sundress, or a cute shift with a splash of bright jewelry," says Swann. If you're celebrating in a tropical locale, break out an exotic print, and maybe tuck a flower in your hair, suggests Mindy Lockard, an etiquette consultant in Portland, Oregon. Whether you're headed to a beach wedding, a rustic rehearsal dinner, or an alfresco luncheon, ditch the heels, which will sink into sand or grass. Gold wedges, beaded sandals, or embellished ballet flats are posh enough for the occasion. Instead of black, pick white or a shade that plays up the natural surroundings—blue, coral, yellow.

Attire for Men:

Leave the serious jacket and tie at home. Instead, "choose an ivory or tan linen suit or a pale shirt with white pants, loafers, and no socks," says Himel. If the setting is a country club, switch to classic preppy: khakis and a pastel oxford shirt with a sport jacket.

Business Dress Code

Business attire, or work-appropriate attire, is anything you would wear to an important interview.

Attire for Women:

For work dinners, company parties, and networking events, gravitate toward Wall Street rather than dot-com. That means a simple, neutral suit or a sheath dress. "Look to Jackie O. for inspiration," Lockard says. This isn't the time to experiment with trendy cuts or the hot color of the season, though you may want to consider adding texture with a metallic tweed or a variegated bouclé jacket or skirt. Even if your office is casual, spiff up your usual look with a skirt rather than pants, a blouse in place of a tee, and pumps over flats. In this case, it's okay to carry your everyday bag.

You can loosen up a bit for a work holiday party and introduce a single touch of sparkle or color. But keep your hemline around the knee and your neckline conservative.

Attire for Men:

"A gray or navy suit is best. Black is too funereal or maître d'–ish," says Himel. A dark chalk-stripe or windowpane pattern works, too. Add a natty tie, a white or pale blue dress shirt, and polished brown shoes.

Smart Casual Dress Code

Smart casual translates to dressy casual or casual chic. Think a dress-up/dress-down hybrid like denim and diamonds.

Attire for Women:

Pair a weekend staple with something glamorous—for instance, jeans with a bow blouse and heeled booties or ornate flats. To look pulled-together in jeans, stick to a deep indigo rinse, a sophisticated pattern, or a saturated shade, like cobalt, oxblood, or emerald. Sharpen up further with a blazer and Golden Globes-worthy earrings. The goal is polished but not uptight, so a floral shift or a pair of tailored pants with a bright cardigan also make the cut, particularly for a daytime function, like a bridal shower.

When it's a girls' night out or a dinner party, you can be more adventurous in a trendy jumpsuit or boldly printed pants. What to do about dress codes that mystifyingly tag "chic" to other words? (As in "California chic," "city chic," "jet-set chic.") Lockard says to go the extra mile if you're at a loss: "Being overdressed shows you put in an effort, whereas being underdressed can come across as disrespectful."

Attire for Men:

"Aim for date night—no suits or ties," says Loose. Sport a tailored oxford shirt with flat-front chinos or sleek wool pants. But if the event is more pub than lounge, switch to dark denim.

Come as You Are (aka Casual Dress Code)

Keep it low-key and comfortable, but try to step it up from yoga pants.

Attire for Women:

Your host may actually be saying, "We're easygoing. Just come on by and don't stress about it." Still, it's worth putting on a touch of makeup, so you don't look as if you just rolled out of bed, says Loose. Something you would put on for lunch with friends—say, nice jeans with a striped top and ballet flats—is ideal. If it's a backyard barbecue, an open house with the neighbors, or a get-together with kids, nice jeans and Converse sneakers or other cute kicks pass muster. It's also smart to take a cue from the host. If she is usually put together on an average day, follow her lead and slip on a simple jersey dress with skimmers or boots. What not to wear, no matter what: gym clothes, like graphic tees, sweats, and beat-up trainers.

Attire for Men:

Everyday clothes that are clean, in good condition, and unwrinkled. (Yep, the bar is pretty low.) Try a Henley or a button-down with jeans or, in the summer, shorts. Whether boots or sneakers, the footwear should be well-kept and stylish to elevate the whole look.

What Does "Black Tie Optional" Really Mean?

When an invitation says a style of dress is "optional" or "preferred," the host is stating their preference, but allowing for some wiggle room. "It means, 'This is what I'd like you to wear, so if you have it, wear it—or the next best thing,'" says etiquette consultant Mindy Lockard. It doesn't mean "Go out and buy a new outfit."

Expect a lot of hemlines that hit around the knee at a black tie–optional affair, says event planner Tara Guérard. But if you do go short, the dress should be awards-show fancy. As for men, a dark, dressy suit with a black tie is acceptable in place of a tux.

And If There's No Dress Code on the Invitation?

Here are five ways to figure out what to wear when no dress code can be found:

Ask the Host: If the invitation offers no heads-up on the attire, the surest way to find out the dress code is to ask the host what she is wearing. But if you don't feel comfortable doing so, you're going to have to play detective. Puzzle it out with friends who are also going to the party and decide on a dress code that you can all agree on. But again, when in doubt, it's better to be overdressed.

Inspect the Invitation: If the invitation is engraved, letterpress, or embossed on nice card stock, the host is probably spending time and money on the event. Acknowledge her efforts with a gown or a cocktail dress. Store-bought cards are trickier to decipher because they vary from extravagant to basic, so search for other possible tip-offs (see below). When dealing with e-vites (which are sent even for weddings these days), look for hints in the design and the wording.

Be Mindful of the Theme: If this is an annual event for a charity or an organization, check out what has been photographed and documented online to guesstimate your getup. Religious ceremonies, like Bar Mitzvahs and baptisms, deserve respect with a more conservative outfit.

Note the Time: As a general rule, parties after 5 p.m. mean more elegant looks, whereas daytime functions tend to be low-key.

Scope Out the Location: A party at someone's house will probably be more relaxed than one at a venue. But if it's at a catering hall or a restaurant, browse the website or take a field trip to gauge its chichi quotient. Outdoor soirees tend to be less formal than indoor functions. Country club protocol, however, leans toward sundresses rather than jeans (sometimes white jeans are OK, but you'll want to double-check before taking that route).