To Fair or Not to Fair. . .

I have never sold at a craft fair. As a matter of fact, I don't recall that I have ever even BEEN to a craft fair. But there is one that is held not too far from here that I really want to be a part of. So, today I am searching for some info. Have any of you ever sold at a craft fair? Has it been worth your while? Do you have any tips, hints, ideas, suggestions? What size booth should I sign up