We did a small show like that one time and a 10x10 is ideal for soaps, as you don't need a lot of room like for birdhouses, etc.
We made our soap displays from lumber at the house. I'll send you a picture. Or you might be able to see them on our flickr page. I think this one is the best.
http://farm4.static.flickr.com/3285/311 ... 620b_m.jpgLittle displays are best. We did a websearch for soap displays and got a lot of good ideas that way.
You'll need nice but inexpensive table covering. We use Mexican style blankets and khaki colored material most times. Christmas lights are cute, or flowers or Easter eggs to throw around with your soaps. We also put things in display baskets if you don't want to purchase wood displays. Baskets are a cheap and easy way to group and display your soaps. We use little gimmicks like "free soap slice samples" or "register to win this gift basket". It gets people to stop and visit, plant the seed about handmade soaps. Let them use a tester if you have lotions or creams. They like that.
You'll need to find out if they have tables furnished, to rent or if you need to bring your own. Is it indoors or outside? Outside and you'll need to see if they have tents provided, for rent or if you need to bring your own. It's a one-time investment if you take care of your folding tent. Bring CHAIRS. You might want to sit at some point. ha
Hope that helps!