Try to find a design which expresses your individuality. The more that a dress reflects your personality and individuality, the less likely that you are to turn up wearing exactly the same outfit as someone else. When looking for an individual item, it can pay off to spend a little bit of time looking around at different stores, or turning to online stores. If there is only one big store in your town, try not to get your dress from there, as it is highly likely that other people will have bought their prom dresses from there too, and may have chosen exactly the same outfits. If you do get your dress from a big chain store, consider visiting a dressmaker, so that it can be customised.
Consult a style guide to see which style will look best on your body shape. Not every girl will look perfect in every dress, because every girl has unique features. Style guides are able to help you to work out which body type you have, and which type of dress would suit this body type best. Choosing the right style of prom dresses will help you to find a piece which accentuates your best features, whilst hiding the features which you feel less confident about. This will help you to feel beautiful and confident for the whole evening.
Comfort should be high on your list. Do not buy a smaller size than you wear, even if you think that you are getting a great deal. Not being able to breathe because of your dress, and passing out on the night because of this is not a great look, and is not something that you will want people to remember you for! Neither is constant itching and scratching. Cheap fabrics can cause itchiness and rashes, especially if you are quite warm, so it is best to look for good quality fabrics.