I've exhibited at both trade (did Harrogate nursery fair a couple of years ago) and 'public' fairs.
Agree with Bellamiller, it's good to treat 'selling to the public' fairs as an advertising opportunity, too. I handed out leaflets with a 10% discount code on to use on the website-I knew a sale had come from the show if they used the code.
Fairs can also be a good networking opportunity- in quiet times you can visit other stall holders and have a chat
- I added a couple of new stockists at a 'sell to the public' show
