FASHION : It’ll Be Baby Dolls for Gals, Sarcasm for Guys This Fall : The feminine look will also encompass the retro newsboy while males share their thoughts on trendy T-shirts.

Guys forward, girls back. The fall dance of fashion calls it out: male back-to-school styles are mod; feminine outfits, retro.

We fashion analysts can explain all of this in terms of social relativism and androgyny backlash--but, why labor with ideological theory? Just go out and get the look.

For teen-agers and young women, you will need: the baby doll, the newsboy or the parochial schoolgirl.

Sounds unlikely? That’s the point--it gets you off guard. Just when you think pleated plaid skirts are as cold as Lurex jumpsuits, they come back for the knockout. (Watch out for Lurex in the spring.)

The plaids are short, boxy and have a keen Highland mood about them. They are combined with plaid tams, plaid vests, occasionally plaid tights (sorry), and often, solid color “baby Ts.”

These are tiny shirts with skimpy, fluted sleeves that come in lengths too short to tuck in. To avoid dress code citations, keep your arms down.

The shirts team with short, sheer jumpers to complete the baby-doll style, or with what one teen-ager called “office skirts”--long, straight ‘50s type skirts given relevance with a slit extending to the thigh.

Skirts, in general, are poised for a comeback after a couple of decades of being mostly invisible on campus.

But, they don’t figure in the most prominent look in local shops--the newsboy. It’s a nostalgic remake of young men’s fashions of the ‘20s. Pin stripes, checks, cuffs on trousers, argyle socks--all in black and white and gray, sometimes with white shirt and tie, the whole set off by a pair of black elastic suspenders.

Without the suspenders, forget it. You may as well wear bell-bottoms minus platforms, or skip the rhinestone trim on your Lurex.

The ensemble is topped with an oversized newsboy cap, a style so appealing it is revived every dozen years or so. In one incarnation it was called the bee bop, but it’s now the Rasta .

As virile as these clothes look, none of them is approved wear for guys. Nor, happily, has male fashion needed to resort to similar cross dressing. Instead, guys are into what they’ve been into all along: sports and wisecracks.

These concerns are addressed as usual by designers’ fusing smart remarks to active wear, and there’s no shortage of choices. But one label in particular kept coming to our attention. Merchants from Bullock’s to JC Penney, plus several teen-agers in the know, responded to “What’s the hottest trend for guys?” with the mantra: “No Fear.”

This upstart company has used the same elements for fall as other manufacturers: soft, washed-out colors, trims of plaid, corduroy or denim on cotton, and contrasting hood fabrics on sweat shirts. They have abetted what might be called the revenge of the horizontal stripe. But, it’s the slogans that sell the line. They produce T-shirt credos that seem to have captured a generation.

“Shut up and jump!” is a classic. It has been joined by such sentiments as, “Quit your snivelin’ and get a life!”; “You don’t need luck if you’re good” and “If you’re not living on the edge, you’re taking up too much space.”

No Fear releases about a dozen new slogans each month, said its art director, Don Widmer, who handles its T-shirt operation. This creative frenzy is in part possible because everyone in the company, including receivers and truck drivers, thinks up remarks to put on shirts. The final messages are chosen for inspirational quality.

“We try to make a statement for everybody who’s not getting out there,” Widmer said. “You know, there’s more to life than what you see on TV. Go out and participate is what we’re saying. You’ve got to go out and do something. But don’t be afraid to do it just because you’ve never done it before.”

This is all well and good, but a central problem remains in the garment industry. Obviously, no one is developing motivational clothing for girls.

To overcome this, we considered offering a slogan to be added to the plaid mini-kilts: “Shut up and eat your oatmeal!” And, as a Jazz Age motto for the suspenders, “Me quit? Banana oil!”

Somehow, these phrases seemed less relevant than those for the boys. The thing is, women aren’t into daring each other to do things--they’re more concerned with expressing their feelings.

So, designers need to concentrate on finding messages that promote emotional sharing, while celebrating a particular era. The suspenders might instead urge: “Verbalize--it’s swell!” or, “Tell it like it is, but speak easy.”

Such sentiment could mean a smash hit for the industry; all they have do is learn to address our basic natures through clothing.