So, you're shopping for your dress, and you've found the perfect one... Hate to be the pessimist, but let's look at all the things that could go wrong.
It doesn't fit.
This problem can happen a lot. Either the dress is too big, or it's too small, obviously. It's better to have the dress be a little bit bigger than it is to have it too snug. When the dress is too big, it's easy to bring it to a tailor and have it tailored so it fits perfectly. But when the dress is too snug, you could bring it to a tailor too, but it's probably a little more difficult for them to let it out. Also, if your dress is too long, a good tailor can take care of that too.
You're shopping online and you don't know what size to get.
Like I said before, it's better to get a slightly bigger size so a tailor can make it fit perfectly. But to avoid that altogether, look at the dress' sizing table, and most likely they'll teach you how to do your measurements. If you're exercising to get in shape for prom, and you can't estimate what size you'll be by the time you order your dress, then go order whatever size you are now. It's a bad feeling ordering the smaller size you think you'll fit into and then not be able to fit into it come prom night. You'd think that it would be good motivation, but it's not really a good way to think.
You don't know what color to choose.
This is my biggest problem with dress shopping, and I know how you feel if you're struggling with this issue. So, you don't know what colors really look fantastic on you. First, you should decide what kind of skin tone you have. Look at the veins on the inside of your wrist. If they're green, then you have yellow undertones, which means your skin tone is warm. If you see blue veins, your skin tone is cool. Another way to determine your skin tone (the vein thing doesn't really work with me, I can never tell) is to see how gold and silver jewelry look on you. If you look better with silver jewelry, you have a cool skin tone, and if you look better with gold jewelry, you have a warm skin tone.
You want a strapless dress, but you also wanna get down on the dance floor.
If you're like me and you love the look of strapless dresses (I love how they make my collarbones look), but you also love dancing with your arms in the air, have no fear. There are a few ways you can get away with going strapless without flashing the entire student body while you're throwing your hands up, cuz they're playing your song (if you got the Classic Miley Cyrus reference, we're automatically best friends). You could go with fashion tape, depending on how heavy your dress is. You should test this out before you're heading out the door to take prom pictures. When you have your dress and you have your tape, put them both on (I find that going braless when using tape is good if you don't wanna deal with two strapless garments slipping around), jump around your room and flail your arms about, and see if the tape can keep everything together. For Junior Prom I had a satin dress with sequins on the bodice, and the weight only gave the fashion tape about 10 minutes of life before I started fidgeting with my dress again. I don't know how it would work with, say, a chiffon dress or something, but by all means, try it out! I've heard stories of people keeping their dresses up by using double sided carpet tape... It works, apparently, but I'd imagine getting that off your boobs would be a real bitch (excuse my French)... Another pretty good idea that I've heard about is taking some Velcro strips and attaching one side to your bra and the other to your dress, and BOOM, you get to wear a bra and flail about on the dance floor.
The method I've heard about that appeals to me the most, though, is using body adhesive. I've come across a little gem called IT Stays Body Adhesive (yes, it's a liquid like glue), and many women swear by it. I say if it can keep up a wedding dress, a prom dress would be easy peasy. If I can't get my hands on that adhesive, I'd just get a dress with thin removable straps and take them off for pre-prom pictures and put them on for the dancing.
These are all the dress prom-blems I can think of for now, leave a comment and I'll add some more later!