Dressing down — for the office, special occasions and even supposed black-tie affairs — has been around so long that today's teenagers and 20-somethings are over it.

Instead of embracing the sloppy look that society has come to expect from its youth, this generation takes pride in pulling its look together. There might not be a better occasion to pull out all the stops than New Year's Eve, when people are in the mood for a party and everyone has that new digital camera tucked in the pocket.

"Young people are really excited about getting dress-ed up," says Eric Daman, costume designer for "Gossip Girl."

But he adds that there's nothing old or stodgy about the new "fancy."

"They like to mix a great little leather jacket with a cocktail dress, or they'll take that leather jacket and make it a New Year's outfit with a sequin blazer, a boy's tank top and skinny jeans and rock 'n' roll boots. They'll take a dress-up item and dress it down just enough," says Daman, whose style-advice book, "You Know You Want It," was just published by Clarkson Potter.

"Gossip Girl" star Leigh-ton Meester writes in the foreword that she had a more casual style before Daman persuaded her to start trying on trends. "I feel so much more comfortable going outside of myself and dressing up; I appreciate designer clothing and beautiful material," she writes.

Spoken like a connoisseur of fashion — and Meester is 23 years old.

And there's no doubt that Meester and co-star Blake Lively are considered trendsetters, with them turning out to attend, say, an afternoon fashion show in a cocktail frock. There's no grunge here as their on- and off-set wardrobes are chronicled by the press.

Perhaps it's not lost on these young stars that the lasting fashion images of the class of celebrities just before them — Lindsay Lohan and Britney Spears included — are mostly disheveled "don'ts."

For 17-year-old Doc Shaw, of Disney Channel's "The Suite Life on Deck," the turning point in his wardrobe came young. "I've been dressing up for years. I like to know I look presentable."

Sure, he was teased a little in his Atlanta-area public school, he says, but now he sees 13- and 14-year-olds trending toward the geek-chic look. Shaw likes to think he was ahead of that curve.

And where did he get the idea that dressing up gets you noticed for the right reasons? Music videos, he says.

Videos also exposed him to the brands that now Shaw rattles off: his David Yurman jewelry, True Religion jeans, Tom Ford suit and Gucci shoes.

"Anywhere you go, you never know what can happen or who is looking at you. I want to look ready," Shaw says.

But even those who needn't fear the paparazzi have bought in to that look-good, get-noticed mentality.

Kyla Normand, 22, of North Kingstown, R.I., says she has always looked pulled together, even when she was still a student at the University of Virginia. The economic downturn has made a professional appearance a must for women her age, she says.

"The population of young people has to brand themselves as more professional and mature and capable of producing the same quality of work as someone with experience," Normand says. "Maybe it's materialistic, but dressing up definitely shows employers that a person values their job."

With her budding TV and music career, "Sonny With a Chance's" Tiffany Thornton, 23, says it's important for her to look the part of a stylish starlet: "I love wearing dresses — and I prefer them for the daytime. At night, I'll wear a little black dress or really nice jeans, a black top and a great pair of heels."

She'll go all out on New Year's, if she decides to go to a party. "You know people will be taking pictures then," she says. If it's a smaller affair, then Thornton will still be in a sparkly top.

"Girls love sparkly stuff — innately," says Daman. But his suggestion for a young woman who really wants to be trend-right going into 2010 would be to wear matte sequins. "There's a contemporary edge to the matte, and a good thing is that it exists as so many price points. It's not like cheap shiny sequins, which can look cheap."