That means you'll need to worry about the entire ensemble: a coordinating manicure, pedicure, purse/clutch, corsage, hair accessories, shoes and jewelry.

But remember that the dress is always the highlight -- the main event. Everything else - including the date - are only minor details.

The dress

• A good fit is always key. Be sure to try on lots of dresses - even those that don't seem to be something that you would like or wear.  Clothing looks totally different on the hanger, than on you! Who knows? You could end up loving that tangerine-colored, satin, skinny-strapped gown that's so NOT your usual color or cut.
• Personal style and taste should reflect your overall look. For example, would you rather have a one-piece dress or are you comfortable in a belly-baring, two-piece ensemble? Long or short? Ball gown-style skirt or slim and straight? Slit or no slit? Covered arms or sleeveless? Plunging neckline or modest?  Sequins, embroidery, or beads?
• Color is definitely an important factor for your dress. Black is a great choice - very chic and sophisticated. Pastels, like pale pink and lavender, are a very common prom color (perfect if you're going for a princess-y, fairy tale look). Bold jewel tones are definitely attention-getting and funky. Show your patriotism in a red or blue dress - if you're especially bold, Jessica McClintock has several red, white, and blue print gowns.  Just be sure you don't look like a flag.
• Beware of overdoing it. Oversized prints, a sparkling dress + lots of jewels, a too-bare ensemb, too much sparkle, painful heels will all ruin your look. Prom is one occasion when less isn't necessarily more (you don't want to look boring!) but you can overdose on frou and flash. 
• Separates are always a great option. For instance, a coral sequin camisole with a coordinating pink satin skirt could be just as striking as a gown (and if you're bold, switch the pink skirt for black for a hip look). Why not try an unexpected combination, like a knit one-shoulder top with a tulle skirt?
• Don't be reluctant to head out of the prom section and into the lingerie department or femme places like Bebe, Express, or even Delias. You can find fab little camisoles and full skirts where you least expect them.
• If you're a little wary of showing your arms, cover up with a little feminine cardigan (not just any would do - make sure it's delicate and color-coordinating) or wrap.

Accessories

• If your dress is simple and understated, add interesting accessories. For example, if you're planning on wearing a gorgeous all-black dress, wear hot pink beaded heels with a hot pink clutch. If you have a glam gown with lots of sequins, beads, color, etc., go easy on accessorizing.
• Either way, accessories are a must. A coordinating clutch or little purse is a necessity.  Anything beaded, sequined, or jeweled is perfect. 
• Of course jewelry completes the look. With a boat or halter neckline, forgo the necklace and don pretty earrings, bracelets, and/or rings. With a strapless or skinny-strap style, you can go with a simple choker or drop necklace. A deep V neck is stunning with a long plunging lariat or short delicate choker.

Shoes

• Shoes are a major factor for the overall look. Heels are ideal, but flats are an alternative, especially for those who seek comfort. Dyed-to-match pumps are an obvious option, but don't limit yourself. Metallic-colored shoes in silver or gold pretty much go with any color (red with gold, lavender with silver, bright pink with silver, et cetera) and are always easy to accessorize with. Another idea would be a coordinated-colored shoe. Choose a different shade of the same color or a complementary color.
• Certain gowns require certain shoes. If your dress is short, low to medium-high heels are best. Low kitten heels to medium-high are great with mid-length skirts. Something ankle-length requires funky mules or backless heels. A floor-grazing gown is best with open-toe slingbacks or stilettos.

Casey is a real, fashion-forward teenage girl who loves clothes (and describes her own look as "trendy prep")  If you want to ask her a question, post it to the Fashion Forum under "Teen" and put "Ask Casey" in the Subject line.