You generally have a space with a table and make it look nice with your leaflets and business cards for people to take. I usually have a banner made up at
http://www.vistaprint.co.uk/gallery...rs+(linked+item)_Signs+&+Banners_All+Products which I attach to my table with my business name and website on etc.
Demos can work, although can't say I've done them myself, but then I do wedding make up and nails etc. I have a portfolio of before and after pics on my desk which people can flick through to give them an idea of what you do.
Another great thing I have found is to do a free prize draw. I usually give away a free manicure for their wedding or something. But it means loads of people will fill in their contact details, which can prove invaluable to add them to a mailing list, or send texts out. And all you have to give away is one treatment.
I have found with wedding fayres, you never can tell how much work you will get from it, but if you can use it to get your name out there and collect in details, it's great.
Even offer a discount for people making bookings on the day. For example, 10% off if you book your pre wedding tan today. Fills up your diary nicely!