Some of the things you can consider include:
Imagery: Basically, the five senses. Most people default to sight, and describe the shape of the dress, but you could easily work in touch, smell and sound too. Taste might be a bit difficult! For example, you might say something like, "The sequins, embedded in the dress and overlapping like fish scales, scintillated their reflections across the room, but they scraped against each other with an unpleasant crackling sound like fingernails being trimmed." You could also choose a less prosaic approach, and say something more like, "The dress was advertised as "sky blue", but in fact was much more pastel and faded. It sat comfortably at ankle height and was, quite frankly, unremarkable as prom dresses go."
Emotion: What is the impact of the dress? Does it have some sentimental value or attachment? The specifics of the dress itself may be unimportant if it represents something greater.
Cultural Significance: Prom dresses are regularly criticized for being too short, revealing or otherwise sexual, depending upon their design and the standards of the community. How does the dress match or defy the cultural standards? Does it make the wearer beautiful or does it represent conformity?
I would think that the instinct in describing a prom dress is in its visual aspects (color, draping, length, possible embellishments, neckline). If you wanted to take a more unique approach to it, here are a couple other possibilities:
- The search: Depending on the community/family/girl, everyone's search for a prom dress is different, and one way to describe a prom dress might be through describing the "quest" to find it - numerous trips to the dressing room before finally finding one that was just right (not too tight, not too loose, not too bright, not too dull, etc.). This approach would be especially effective if the search was particularly frustrating, I would think.
- How it feels to wear the prom dress: This could be very positive, as in "I found the perfect dress and felt so confident in the dress, which only added to my prom experience". However, it could also come off with a slight negative slant, as in "The dress was beautiful in the mirror, but had it always been this tight and itchy in that one spot on my back where I can't reach?"
Things to consider:
- length (long, short, above the knee)
- type of fabric used (silk, cotton, etc)
- neckline (sweetheart, v-neck, tube, sleeveless)
- details/accessories (sequins, ribbons, lace, etc.)
- drapery (flowy, corset-type, fitted)
I agree that using the five senses is a great way to describe a prom dress (or anything really). You need to include what the dress looks like (Is it long or short? Does it have a lot of glitter or sequins? Is it a bright of neutral color?), how it feels texture wise, and how the dress feels when worn. Just be descriptive when it comes to color and looks as well as add details about the overall feel of the dress.
I think that caledon's answer is wonderful! I wholeheartedly agree that including the senses in your essay is a great way to describe the dress. I also think that it would be best to include how the dress makes you feel, especially if it's your own. Also I think you should include perhaps other people's view on the dress. Getting a different POV on something is a great way to describe it in a different light. If you can't get another person's personal opinion in there, another great way is to simply observe other people's actions and feelings towards the dress, and include those in your essay.