SHOP TALK : Knowing Basics Will Guide You Through Forest of Formal Wear : If you have to rent a tuxedo, it helps to know what’s trendy and where to find discounts. This year, vests are popular.

Tuxedo rentals. Most guys have to go through that rite of manhood at some point during their teen-age years.

Unfortunately, that first mention of tuxedo and rental often is followed by the word yeeecchhh . Until, of course, the fine threads are put on, and suddenly the wearer is overcome with a feeling of maturity far beyond his years.

Well, it’s now May, and that means a whole new crop of guys will be entering the tuxedo rental market in preparation for various junior and senior proms. And we are going to lend a helping hand because the world of fancy clothes is scary if you’ve never visited it before.

One thing you must know is that tuxedo rental businesses are not listed under “Tuxedos” in the Pacific Bell and GTE yellow pages. They are listed under “Formal Wear Rental,” which is right after “Fork Lift Rental.”

We checked around to see what was available to rent (tuxedos, not fork lifts), and to get some tips from the experts.

First, let’s relieve some of the pressure: There doesn’t seem to be much of a price variance from operation to operation. Expect to find the regular rate of a basic black tuxedo package to be about $50 to $55 wherever you go. Now, remember, the minimum price is for basic black. Prices can range up to about $80 depending on how designer-chic you want to get.

What you’ll really want to consider, however, is that many places offer prom discounts. And discount policies vary.

We checked with Whitehall Clothiers in Camarillo, Gingiss Formalwear in Thousand Oaks, and in Ventura, both Paramount Cleaners and Classic Cleaners, which are under the same ownership.

Whitehall gives 10% off the usual $49-$75 price for any student going to a prom. Gingiss rents any style tuxedo--even those at the more expensive end--for $55 to students from Thousand Oaks, Simi Valley, Moorpark and Camarillo. Students from other areas may not get the $55 rate, but will get 20% off.

And at the two cleaners, where the range is $55-$80, there’s a 20% discount--if you ask for it or bring in one of the store’s discount coupons.

When we talk about the cost of tuxedo rental, we’re generally talking about the basic jacket, tie, shirt, vest, cummerbund, cuff links--everything but the shoes. Shoes are extra. Whitehall has them for $10, Gingiss has them for $12, and at the cleaners they go for $11. But of course, shoe rental is optional.

“Some kids are going with their own shoes, which I guess is a trend,” said Monika Newman, the store manager at Gingiss. “I’m not sure if they’re just trying to be different or if it’s to conserve price.” One added cost that is not optional is the damage waiver fee. Again, stores don’t vary much in this area. At the cleaners and at Whitehall it’s $5; at Gingiss it’s $3.

Now that your cost fears either have been alleviated or heightened, let’s take a quick look at what’s in style.

“What we are doing a lot now is renting the basic black tuxedo and customizing the look with a designer vest. Vests are very popular,” said Keith White, owner of Whitehall. “So, instead of renting an $80 designer tuxedo, you can rent the opening price tuxedo for $45 and then rent a $5 vest.”

Just so you know, the “in” design in vests involves patterns and bold colors. And when we say colors, we’re talking red, purple, teal--the gamut. White said the vest is a good way to pick up the accent in the color of your date’s dress. And remember, guys, you do want to coordinate with her.

Newman said she has also seen an increase in the popularity of the vest, and the kids renting from the two cleaners in Ventura generally are going with the more conservative black outfit.

So there you have it--pretty much set to rent that tuxedo. The tricky part is finding someone to go with to the prom.