Even if you have straight hair, you'll want to iron it and spray on shine serum to get a maximum sleek look. The secret to this style is curlers and hairpins. Once the curls are made, you'll want to pin them in place (again long, straight hairpins are best, see other hairstyles before this one on how to use them and where to get them), then spray. Again, don't make the mistake of making your updo stiff and tacky with heavy-duty hairspray. You'll want a flexible hold formula that can withstand humidity, but leaves hair touchable.
See dozens more gorgeous prom hairstyles here.
See dozens more gorgeous prom hairstyles here.

