This Halloween, don’t make Cady Heron’s mistake of dressing up in a full-length Bride of Frankenstein outfit. Your costume is a license to be the person you can’t during class, at the library or in the dining hall, so make the most of it. Consult the following guide to making your Halloween costume less trick and much, much more treat.

The basic rules

To make any outfit more provocative for guys and girls, unbutton, unzip or untuck. It’s easy to take clothes you already own and make them sexy-Halloween appropriate: mess with them and show more skin than usual. Not only is this especially easy to do with button-down shirts and skirts, these simple modifications won’t blow your Halloween/Parents’ Weekend budget.

Where to shop

If you’ve already exhausted the possibilities in your closet, downtown Evanston has some very simple Halloween solutions. Your best option? American Apparel. The store has received negative press about its scandalous ads and the salacious behavior of founder Dov Charney — which makes it the perfect place to shop for a sexy Halloween outfit!

It’s a bit on the pricey side, especially for selling so much cheap cotton and spandex, but its made-in-the-USA goodness combined with the variety of wardrobe staples means it will last you beyond Oct. 31.

A prime example of what not to do when you’re sexifying your Halloween costume.

Sweetly angelic/Delightfully devilish

American Apparel employee Erica Polacek, who has worked in the Evanston location for a year and a half, recommends their Shiny High-Waist Skirt ($44) because it can be worn as a cape, dress or a skirt, making it wearable for parties on both Friday and Saturday nights. In the same vein, their Stretch Velvet Double U-Neck Long Sleeve Mini ($42) is “short, tight and sexy as a dress” and can double as a shirt when the weekend is over, Polacek says. The colors lend themselves to different costumes, like “champagne luster” for an angelic feel or the non-shiny high-waist skirt in red for a devil.

Animal behavior

Other options at the store include their vast section of lamé — “Our lamé leggings are always a big hit,” says Polacek. Pair a print with furry ears and a fuzzy tail to transform yourself into the animal of your choice, or use the lamè mini or hot pants for a superhero.

Back to the future: 1980s

If you feel like sexing up your shoulder pads, go with an ‘80s theme. The boxy blazers and shiny shirts at many nearby stores, like Urban Outfitters or Forever21, could make 2009 a banner year for a flashback. American Apparel has you covered in the ‘80s department, too — their cropped shirts, high legwarmers and shiny headbands over a bright bodysuit would make you the best-looking aerobics instructor since Jane Fonda.

The lamè jackets also work for guys and girls alike to create a hokey throwback vibe.

Pop’s newest creation

If you’ve spent the last few weeks perfecting your hot bod at SPAC’s free classes, but dressing up like you’re about to go to a jazzercise class isn’t your thing, try a Lady Gaga costume. Pull American Apparel’s Polyester Spandex Shiny Stripe Tank Bodysuit ($34) over some Opaque Tights ($14) with fingerless gloves, high heels or thigh-high boots and as many accessories as you can pile on to imitate the performer’s crazy look. You can grab a GaGa wig at any Halloween store, and with some bright lipstick you’ll definitely look the eye-catching part. Your look can easily be transformed into a Madonna costume for another Halloween party by adding jelly bracelets, fishnet tights and converse sneakers, with a few Malawian babies on the side.

As you prepare for the one night where the usual rules of decency don’t apply, take a chance on some scandal. You can still scare your friends with vampire fangs and dripping fake blood, but only if you unbutton the top of your high-necked Victorian collar.