Well, like most parties, you should make sure you have enough food and drinks for the guests.
Plus, being a clothes party, you need to make sure there's a "changing room" and a mirror available (preferably full length). You could borrow a mirror from someone if you only have small mirrors in your house.
It's also important that you have plenty of seating, where the guests can see the clothes so no one has to crane their necks to see, or miss out on seeing the clothes.
Also having plenty of pens on hand as well as something to lean, for when the guests are filling out their order forms is handy (if applicable).
Hopefully this helps you a bit!
Don't stress though, I'm sure it'll go smoothly.